By 2011, all remnants of "Timmy" seemed to be gone. When his close friend and sparring partner Brendan Mess began dating a nonpracticing Muslim, Tamerlan criticized Mess' girlfriend for her lack of modesty. And he also reportedly criticized Mess for his "lifestyle" – he was a local pot dealer. On September 11th, 2011 – the 10th anniversary of 9/11 – Mess and two of his friends were killed in a grisly triple murder that remains unsolved. Since the bombing, authorities have been vigorously investigating the crime, convinced that Tamerlan had something to do with it, though so far there's no hard evidence.

"All I know is Jahar was really wary of coming home high because of how his brother would react. He'd get really angry," says Will. "He was a really intense dude."

"And if you weren't Muslim, he was even more intense," says Sam, who notes that he never met Tamerlan in person, though he heard stories about him all the time from Jahar. "I was fascinated – this dude's, like, six-three, he's a boxer – I wanted to meet him," says Sam. "But Jahar was like, 'No, you don't want to meet him.'"

He rarely spoke to his friends about his sisters, Ailina and Bella, who, just a few years older than he, kept to themselves but also had their own struggles. Attractive, dark-haired girls who were "very Americanized," as friends recall, they worshipped Tamerlan, whom one sister would later refer to as her "hero" – but they were also subject to his role as family policeman. When Bella was a junior in high school, her father, hearing that she'd been seen in the company of an American boy, pulled her out of school and dispatched Tamerlan to beat the boy up. Friends later spotted Bella wearing a hijab; not long afterward, she disappeared from Cambridge entirely. Some time later, Ailina would similarly vanish. Both girls were reportedly set up in arranged marriages.

Anna Nikeava was unaware the girls had even left Boston, and suspects the parents never talked about it for fear of being judged. "Underneath it all, they were a screwed-up family," she says. "They weren't Chechen" – they had not come from Chechnya, as she and others had – "and I don't think the other families accepted them as Chechens. They could not define themselves or where they belonged. And poor Jahar was the silent survivor of all that dysfunction," she says. "He never said a word. But inside, he was very hurt, his world was crushed by what was going on with his family. He just learned not to show it."
Anzor, who'd been at first baffled, and later "depressed," by his wife's and son's religiosity, moved back to Russia in 2011, and that summer was granted a divorce. Zubeidat was later arrested for attempting to shoplift $1,600 worth of clothes from a Lord & Taylor. Rather than face prosecution, she skipped bail and also returned to Russia, where she ultimately reconciled with her ex-husband. Jahar's sisters, both of whom seemed to have escaped their early marriages, were living in New Jersey and hadn't seen their family in some time.

And Tamerlan was now married, too. His new wife, Katherine Russell, was a Protestant from a well-off family in Rhode Island. After high school, she'd toyed with joining the Peace Corps but instead settled on college at Boston's Suffolk University. She'd met Tamerlan at a club during her freshman year, in 2007, and found him "tall and handsome and having some measure of worldliness," one friend would recall. But as their relationship progressed, Katherine's college roommates began to worry that Tamerlan was "controlling" and "manipulative." They became increasingly concerned when he demanded that she cover herself and convert to Islam.

Though Katherine has never spoken to the press, what is known is that she did convert to Islam, adopting the name "Karima," and soon got pregnant and dropped out of college. In June 2010, she and Tamerlan were married; not long afterward, she gave birth to their daughter, Zahira. Around this time, both her friends and family say, she "pulled away." She was seen in Boston, shopping at Whole Foods, cloaked and wearing a hijab. She rarely spoke around her husband, and when alone, recalls one neighbor, she spoke slowly with an accent. "I didn't even know she was an American," he says.

Jahar, meanwhile, was preparing for college. He had won a $2,500 city scholarship, which is awarded each year to about 40 to 50 Cambridge students; he ended up being accepted at a number of schools, including Northeastern University and UMass Amherst. But UMass Dartmouth offered him a scholarship. "He didn't want to force his parents to pay a lot of money for school," says Sam, who recalls that Jahar never even bothered to apply to his fantasy schools, Brandeis and Tufts, due to their price tags. A number of his friends would go off to some of the country's better private colleges, "but Jizz rolled with the punches. He put into his head, 'I can't go to school for mad dough, so I'm just going to go wherever gives me the best deal.' Because, I mean, what's the point of going to a school that's going to cost $30,000 a year – for what? Pointless." His other friends agree.

A middling school an hour and a half south of Boston, UMass Dartmouth had one distinguishing feature – its utter lack of character. "It's beige," says Jackson. "It's, like, the most depressing campus I've ever seen." Annual costs are about $22,000.

Jahar arrived in the fall of 2011 and almost immediately wanted to go home. North Dartmouth, where the university is based, is a working-class community with virtually nothing to boast of except for a rather sad mall and a striking number of fast-food joints. It has a diverse student population, but their level of curiosity seemed to fall far below his friends' from Rindge. "Using my high-school essays for my english class #itsthateasy," Jahar tweeted in November 2011. "You know what i like to do? answer my own questions cuz no one else can."
"He was hating life," says Sam. "He used to always call and say it's mad wack and the people were corny." His one saving grace was that one of his best friends from Rindge had gone to UMass Dartmouth, too – though he would later transfer. "All they would do was sit in the car and get high – it was that boring," says Sam.

On the weekends, campus would empty out and Jahar came home as often as he could. But home was no longer "home," as his parents were gone. Many of his closest friends were gone as well. Tamerlan, though, was always around. "Pray," the older brother told the younger. "You cannot call yourself a Muslim unless you thank Allah five times a day."

Much of what is known about the two years of Jahar's life leading up to the bombing comes from random press interviews with students at UMass Dartmouth, none of whom seemed to have been particularly close with Jahar; and from Jahar's tweets, which, like many 18- or 19-year-olds', were a mishmash of sophomoric jokes, complaints about his roommate, his perpetual lateness, some rap lyrics, the occasional deep thought ("Find your place and your purpose and make a plan for the future") and, increasingly, some genuinely revealing statements. He was homesick. He suffered from insomnia. He had repeated zombie dreams. And he missed his dad. "I can see my face in my dad's pictures as a youngin, he even had a ridiculous amount of hair like me," he tweeted in June 2012.

Jahar had begun his studies to be an engineer, but by last fall had found the courses too difficult. He switched to biology and, to make money, he dealt pot – one friend from his dorm says he always had big Tupperware containers of weed in his fridge.

As he had at Rindge, Jahar drifted between social groups, though he clung to friends from high school who also attended UMass Dartmouth. But he soon gravitated to a group of Kazakh students, wealthy boys with a taste for excellent pot, which Jahar, who spoke Russian with them, often helped to provide. By his sophomore year, even as he gained U.S. citizenship, he abandoned his American Facebook for the Russian version, Vkontakte, or VK, where he listed his religion as "Islam" and his interests as "career and money." He joined several Chechnya-related groups and posted Russian-­language-joke videos. "He was always joking around, and often his jokes had a sarcastic character," says Diana Valeeva, a Russian student who befriended Jahar on VK. Jahar also told Diana that he missed his homeland and would happily come for a visit. "But he did not want to return forever," she says.

Tamerlan's journey the past two years is far easier to trace. Though no more Chechen than his brother, Tamerlan was also – as his resident green card reminded him – not really an American. Islam, or Tamerlan's interpretation of it, had become his identity. He devoured books on Chechnya's separatist struggle, a war that had taken on a notably fundamentalist tone since the late 1990s, thanks to a surge of Muslim fighters from outside of the Caucusus who flocked to Chechnya to wage "holy war" against the Russians. It is not uncommon for young Chechen men to romanticize jihad, and for those who are interested in that kind of thing, there are abundant Chechen jihadist videos online that reinforce this view. They tend to feature Caucasian fighters who, far from the lecturing sheikhs often found in Al Qaeda recruitment videos, look like grizzled Navy SEALs, humping through the woods in camouflage and bandannas. Tamerlan would later post several of these videos on his YouTube page, as well as "The Emergence of Prophecy: The Black Flags from Khorasan," a central part of Al Qaeda and other jihadist mythology, which depicts fierce, supposedly end-times battles against the infidels across a region that includes parts of Afghanistan, Pakistan and Iran.

But Brian Glyn Williams, a professor of Islamic studies at UMass Dartmouth and an expert on terrorism and the politics of Chechnya, believes that Tamerlan's journey – which he calls "jihadification" – was less a young man's quest to join Al Qaeda than to discover his own identity. "To me, this is classic diasporic reconstruction of identity: 'I'm a Chechen, and we're fighting for jihad, and what am I doing? Nothing.' It's not unlike the way some Irish-Americans used to link Ireland and the IRA – they'd never been to Northern Ireland in their lives, but you'd go to certain parts of Southie in Boston, and all you see are donation cans for the IRA."

For Jahar, identity likely played into the mix as well, says Williams, who, though he never met Jahar at UMass Dartmouth, coincidentally corresponded with him during his senior year of high school. One of Williams' friends taught English at Rindge, and "he told me he had this Chechen kid in his class who wanted to do his research paper on Chechnya, a country he'd never lived in." Williams agreed to help Jahar. "The thing that struck me was how little he actually knew," he says. "He didn't know anything about Chechnya, and he wanted to know everything."

Whether Jahar gained much from his studies – or even did much of it – is unknown. Tamerlan, having devoured all the books he could find, was preparing to take the next step. In January 2012, he traveled to Dagestan, where he spent six months. Dagestan has been embroiled in a years-long civil war between Muslim guerrillas and the (also Muslim) police, as well as Russian forces. Bombs go off in the streets regularly, and young men, lured by the romance of the fight, often disappear to "go to the forest," a euphemism for joining the insurgency. Tamerlan, too, seemed to have wanted to join the rebellion, but he was dissuaded from this pursuit by, among others, a distant cousin named Magomed Kartashov, who also happened to be a Dagestani Islamist. Kartashov's Western cousin, who came to Dagestan dressed in fancy American clothes and bragging of being a champion boxer, had no place in their country's civil war, he told Tamerlan. It was an internal struggle – in an interview with TIME magazine, associates of Kartashov's referred to it as "banditry" – and had only resulted in Muslims killing other Muslims. Kartashov urged Tamerlan to embrace nonviolence and forget about Dagestan's troubles. By early summer, Tamerlan was talking about holy war "in a global context," one Dagestani Islamist recalls.

In July 2012, Tamerlan returned to Cambridge. He grew a five-inch beard and began to get in vocal debates about the virtues of Islam. He vociferously criticized U.S. policy in the Middle East. Twice over the next six or eight months, he upset services at a local mosque with a denunciation of Thanksgiving, and also, in January 2013, of Martin Luther King Jr.

The boys' uncle Ruslan hoped that Jahar, away at school, would avoid Tamerlan's influence. Instead, Jahar began to echo his older brother's religious fervor. The Prophet Muhammad, he noted on Twitter, was now his role model. "For me to know that I am FREE from HYPOCRISY is more dear to me than the weight of the ENTIRE world in GOLD," he posted, quoting an early Islamic scholar. He began following Islamic Twitter accounts. "Never underestimate the rebel with a cause," he declared.

Though it seems as if Jahar had found a mission, his embrace of Islam also may have been driven by something more basic: a need to belong. "Look, he was totally abandoned," says Payack, who believes that the divorce of his parents and their subsequent move back to Russia was pivotal, as was the loss of the safety net he had at Rindge.

Theo, who goes to college in Vermont and is one of the few of Jahar's friends to not have any college loans, can't imagine the stress Jahar must have felt. "He had all of this stuff piled up on his shoulders, as well as college, which he's having to pay for himself. That's not easy. All of that just might make you say 'Fuck it' and give up and lose faith.

Wick Sloane, an education advocate and a local community-college professor, sees this as a widespread condition among many young immigrants who pass through his classrooms. "All of these kids are grateful to be in the United States. But it's the usual thing: Is this the land of opportunity or isn't it? When I look at what they've been through, and how they are screwed by federal policies from the moment they turn around, I don't understand why all of them aren't angrier. I'm actually kind of surprised it's taken so long for one of these kids to set off a bomb."

"A decade in America already," Jahar tweeted in March 2012. "I want out." He was looking forward to visiting his parents in Dagestan that summer, but then he learned he wouldn't receive his U.S. passport in time to make the trip. "#Imsad," he told his followers. Instead, he spent the summer lifeguarding at a Harvard pool. "I didn't become a lifeguard to just chill and get paid," Jahar tweeted. "I do it for the people, saving lives brings me joy." He was living with Tamerlan and his sister-in-law, who were going through their own troubles. Money was increasingly tight, and the family was on welfare. Tamerlan was now a stay-at-home dad; his wife worked night and day as a home-health aide to support the family.

Tamerlan had joined an increasing number of Cambridge's young adults who were being priced out due to skyrocketing real-estate prices. "It's really hard to stay in Cambridge because it's becoming so exclusive," says Tamerlan's former Rindge classmate Luis Vasquez, who is running for a seat on the Cambridge City Council. "We feel like we're being taken over."

In August, Jahar, acutely aware of the troubles all around him, commented that $15 billion was spent on the Summer Olympics. "Imagine if that money was used to feed those in need all over the world," he wrote. "The value of human life ain't shit nowadays that's #tragic." In the fall, he returned to North Dartmouth and college, where, with no Tamerlan to catch him, he picked up his life, partying in his dorm and letting his schoolwork slide.

"Idk why it's hard for many of you to accept that 9/11 was an inside job, I mean I guess fuck the facts y'all are some real #patriots #gethip," Jahar tweeted. This is not an uncommon belief. Payack, who also teaches­ writing at the Berklee College of Music, says that a fair amount of his students, notably those born in other countries, believe 9/11 was an "inside job." Aaronson tells me he's shocked by the number of kids he knows who believe the Jews were behind 9/11. "The problem with this demographic is that they do not know the basic narratives of their histories – or really any narratives," he says. "They're blazed on pot and searching the Internet for any 'factoids' that they believe fit their highly de-historicized and decontextualized ideologies. And the adult world totally misunderstands them and dismisses them – and does so at our collective peril," he adds.

Last December, Jahar came home for Christmas break and stayed for several weeks. His friends noticed nothing different about him, except that he was desperately trying to grow a beard – with little success. In early February, he went back to Rindge to work with the wrestling team, where he confided in Theo, who'd also come back to help, that he wished he'd taken wrestling more seriously. He could have been really good had he applied himself a bit more.
At 410 Norfolk St., Tamerlan, once a flashy dresser, had taken to wearing a bathrobe and ratty sweatpants, day after day, while Jahar continued to explore Islam. "I meet the most amazing people," he tweeted. "My religion is the truth."
But he also seemed at times to be struggling, suggesting that even his beloved Cambridge had failed him in some way. "Cambridge got some real, genuinely good people, but at the same time this city can be fake as fuck," he said on January 15th. Also that day: "I don't argue with fools who say Islam is terrorism it's not worth a thing, let an idiot remain an idiot."

According to a transcript from UMass Dartmouth, reviewed by The New York Times, Jahar was failing many of his classes his sophomore year. He was reportedly more than $20,000 in debt to the university. Also weighing on him was the fact that his family's welfare benefits had been cut in November 2012, and in January, Tamerlan and his wife reportedly lost the Section 8 housing subsidy that had enabled them to afford their apartment, leaving them with the prospect of a move.

Why a person with an extreme or "radical" ideology may decide to commit violence is an inexact science, but experts agree that there must be a cognitive opening of some sort. "A person is angry, and he needs an explanation for that angst," explains the Soufan Group's Tom Neer. "Projecting blame is a defense mechanism. Rather than say, 'I'm lost, I've got a problem,' it's much easier to find a conven­ient enemy or scapegoat. The justification comes later – say, U.S. imperialism, or whatever. It's the explanation that is key."

For Tamerlan Tsarnaev, the explanation for his anger was all around him. And so, dissuaded from his quest to wage jihad in Dagestan, he apparently turned his gaze upon America, the country that, in his estimation, had caused so much suffering, most of all his own.

In early February, soon after losing his housing subsidy, Tamerlan drove to New Hampshire, where, according to the indictment, he purchased "48 mortars containing approximately eight pounds of low-explosive powder." Also during this general period, Jahar began downloading Islamic militant tracts to his computer, like the first issue of the Al Qaeda magazine Inspire, which, in an article titled "Make a Bomb in the Kitchen of Your Mom," offered detailed instructions on how to construct an IED using a pressure cooker, explosive powder from fireworks, and shrapnel, among other readily available ingredients.

Jahar returned home for spring break in March and spent time hanging out with his regular crew. He brought his friend Dias Kadyrbayev home with him, driving Dias' flashy black BMW with the joke license plate TERRORISTA. He hung out with a few friends and went to the Riv, where they lit off fireworks; he met other friends at a local basketball court, one of his usual haunts. He looked happy and chill, as he always did, and was wearing a new, brown military-style jacket that his friends thought was "swag." "And that was the last time I saw him," says Will.

What went on in the apartment at 410 Norfolk during March and early April remains a mystery. "It's hard to understand how there could be such disassociation in that child," says Aaronson, who last saw Jahar in January, presumably before the brothers' plan was set. "They supposedly had an arsenal in that fucking house! In the house! I mean, he could have blown up my whole fucking block, for God's sakes."

According to the indictment, the brothers went to a firing range on March 20th, where Jahar rented two 9mm handguns, purchased 200 rounds of ammunition and engaged in target practice with Tamerlan. On April 5th, Tamerlan went online to order electronic components that could be used in making IEDs.

Friends of Jahar's would later tell the FBI that he'd once mentioned he knew how to build bombs. But no one seemed to really take it all that seriously.

"People come into your life to help you, hurt you, love you and leave you and that shapes your character and the person you were meant to be," Jahar tweeted on March 18th. Two days later: "Evil triumphs when good men do nothing."

April 7th: "If you have the knowledge and the inspiration all that's left is to take action."
April 11th: "Most of you are conditioned by the media."
The bombs went off four days later.

On the afternoon of April 18th, Robel Phillipos, a friend of Jahar's from Cambridge as well as from UMass Dartmouth, was watching the news on campus and talking on the phone with Dias. He told Dias, who was in his car, to turn on the TV when he got home. One of the bombers, he said, looked like Jahar. Like most of their friends, Dias thought it was a coincidence and texted Jahar that he looked like one of the suspects on television. "Lol," Jahar wrote back, casually. He told his friend not to text him anymore. "I'm about to leave," he wrote. "If you need something in my room, take it."

According to the FBI, Robel, Dias and their friend Azamat met at Pine Dale Hall, Jahar's dorm, where his roommate informed them that he'd left campus several hours earlier. So they hung out in his room for a while, watching a movie. Then they spotted Jahar's backpack, which the boys noticed had some fireworks inside, emptied of powder. Not sure what to do, they grabbed the bag as well as Jahar's computer, and went back to Dias and Azamat's off-campus apartment, where they "started to freak out, because it became clear from a CNN report . . . that Jahar was one of the Boston Marathon bombers," Robel later told the FBI.
But no one wanted Jahar to get in trouble. Dias and Azamat began speaking to each other in Russian. Finally, Dias turned to Robel and asked in English if he should get rid of the stuff. "Do what you have to do," Robel said. Then he took a nap.

Dias later confessed that he'd grabbed a big black trash bag, filled it with trash and stuffed the backpack and fireworks in there. Then he threw it in a dumpster; the bag was later retrieved from the municipal dump by the FBI. The computer, too, was eventually recovered. Until recently, its contents were unknown.
The contents of Jahar's closely guarded psyche, meanwhile, may never be fully understood. Nor, most likely, will his motivations – which is quite common with accused terrorists. "There is no single precipitating event or stressor," says Neer. "Instead, what you see with most of these people is a gradual process of feeling alienated or listless or not connected. But what they all have in common is a whole constellation of things that aren't working right."

A month or so after the bombing, I am sitting on Alyssa's back deck with a group of Jahar's friends. It's a lazy Sunday in May, and the media onslaught has died down a bit; the FBI, though, is still searching for the source of the brothers' "radicalization," and Al Qaeda in the Arabian Peninsula, capitalizing on the situation, has put Tamerlan, dressed in his crisp, white Saturday Night Fever shirt and aviator shades, in the pages of its most recent Inspire. Jahar has a growing and surprisingly brazen fan club – #FreeJahar – and tens of thousands of new Twitter followers, despite the fact that he hasn't tweeted since before his arrest.

Like so many of his fans, some of Jahar's friends have latched onto conspiracy theories about the bombing, if only because "there are too many unanswered questions," says Cara, who points out that the backpack identified by the FBI was not the same color as Jahar's backpack. There's also a photo on the Internet of Jahar walking away from the scene, no pack, though if you look closely, you can see the outline of a black strap. "Photoshopped!" the caption reads.
Mostly, though, his friends are trying to move on. "We're concerned with not having this tied to us for the rest of our lives," says Alyssa, explaining why she and Sam and Jackson and Cara and Will and James and Theo have insisted I give them pseudonyms. Even as Jahar was on the run, his friends started hearing from the FBI, whose agents shortly descended upon their campuses – sometimes wearing bulletproof vests – looking for insight and phone numbers.

"You're so intimidated, and you think if you don't answer their questions, it looks suspicious," says Jackson, who admits he gave up a number of friends' phone numbers after being pressed by the FBI.

Sam says he thinks the feds tapped his phone. All of the kids were interviewed alone, without a lawyer. "I didn't even know I could have a lawyer," says Jackson. "And they didn't tell me that anything I said might be used against me, which was unfair, because, I mean, I'm only 19."

But the worst, they all agree, is Robel, who was interviewed four times by the FBI, and denied he knew anything until, on the fourth interview, he came clean and told them he'd helped remove the backpack and computer from Jahar's dorm room. Robel is 19 but looks 12, and is unanimously viewed by his friends as the most innocent and sheltered of the group. He is now facing an eight-year prison sentence for lying to a federal officer.

"So you see why we don't want our names associated," says Sam. "It's not that we're trying to show that we're not Jahar's friends. He was a very good friend of mine."

Jahar is, of course, still alive – though it's tempting for everyone to refer to him in the past tense, as if he, too, were dead. He will likely go to prison for the rest of his life, which may be his best possible fate, given the other option, which is the death penalty. "I can't wrap my head around that," says Cara. "Or any of it."
Nor can anyone else. For all of their city's collective angst and community processing and resolutions of being "one Cambridge," the reality is that none of Jahar's friends had any idea he was unhappy, and they really didn't know he had any issues in his family other than, perhaps, his parents' divorce, which was kind of normal.

"I remember he was upset when his dad left the country," says Jackson. "I remember he was giving me a ride home and he mentioned it."
"Now that I think about that, it must have added a lot of pressure having both parents be gone," says Sam.

"But, I mean, that's the mystery," says Jackson. "I don't really know." It's weird, they all agree.
"His brother must have brainwashed him," says Sam. "It's the only explanation."
Someone mentions one of the surveillance videos of Jahar, which shows him impassively watching as people begin to run in response to the blast. "I mean, that's just the face I'd always see chilling, talking, smoking," says Jackson. He wishes­ Jahar had looked panicked. "At least then I'd be able to say, 'OK, something happened.' But . . . nothing."

That day's Boston Globe has run a story about the nurses at Beth Israel Deaconess Hospital who took care of Jahar those first few days after his capture. They were ambivalent, to say the least, about spending too much time with him, for fear of, well, liking him. One nurse said she had to stop herself from calling him "hon." The friends find this story disgusting. "People just have blood in their eyes," says Jackson.

One anecdote that wasn't in the article but that has been quietly making its way around town, via one of his former nurses, is that Jahar cried for two days straight after he woke up in the hospital. No one in the group has heard this yet, and when I mention it, Alyssa gives an anguished sigh of relief. "That's good to know," she says.

"I can definitely see him doing that," says Sam, gratefully. "I hope he's crying. I'd definitely hope . . ."

"I hope he'd wake up and go, 'What the fuck did I do the last 48 hours?' " says Jackson, who decides, along with the others, that this, the crying detail, sounds like Jahar.

But, then again, no one knows what he was crying about.

By Janet Reitman

This story is from the August 1st, 2013 issue of Rolling Stone