In America, he had been a cocky and charismatic heavyweight boxer who wore fancy pointy leather shoes and slick white shirts down to the gym.
In Dagestan, the volatile southern Russian region where he lived for a time as a teen and returned to spend the first half of 2012, he became a quiet young man who spent his days online studying Islam, nursing a growing anger against heretics.
Exactly what turned Tamerlan Tsarnaev into the suspect accused of three murders and mass wounding in the Boston Marathon bombings may never be known. He died in a gunfight with police leaving no explanation. His younger brother and alleged co-conspirator Dzhokhar is in hospital, barely able to speak.
But a picture has emerged in the days since Tamerlan was killed of a proud but angry young man who never quite achieved his own idea of the American dream, but found solace instead in a radical form of Islam adopted by fighters in his homeland.
What now seems clear is that he was deeply influenced by a few months' sojourn in Makhachkala, Muslim Dagestan's capital on the Caspian Sea, where children in the street play "cops and guerrillas" and bombings and shootings are everyday news.
"His radical turn could very well have happened here," Dagestani sociologist Zaid Abdulagatov said. "The Islam that we have in Dagestan today is very tough, very politicized, very dark at times."
As in the cases of other now infamous young men from immigrant backgrounds - like France's Mohammed Merah, who died in a shootout with police a year ago after killing seven people on a gun rampage in Toulouse - it may be impossible to disentangle the psychological demons from political motives.
"It's a complicated mix of reasons, usually as much personal as they are transnational or global," says Rafaello Pantucci, who studies such cases at London's United Royal Services Institute, a defense and security think tank.
"Profiles are almost impossible to draw," he said. "They tend to be under a certain age and are Muslim males. There is usually some kind of outside contact that pushes them along."
This broad pattern seems to have fit the Tsarnaev brothers, ethnic Chechens raised in volatile southern Russia and in Massachusetts by parents who emigrated to seek a better life but never quite made it.
Their father, Anzor Tsarnaev, had held high-status government jobs in the central Asian former Soviet state of Kyrgyzstan, but eventually found work as a mechanic in Massachusetts. Their mother, Zubeidat Tsarnayeva, increasingly turned to religion.
The parents eventually split up and moved back to Dagestan in southern Russia, although their mother was in the United States as recently as last June, when she was arrested by police in Natick, Massachusetts and charged with stealing women's clothing valued at $1,624 from a Lord & Taylor store.
She was also charged with two counts of malicious damage to property after allegedly trying to remove the anti-theft sensors on the clothing, said Lieutenant Brian Grassey of the Natick police. He had no information on the outcome of the case.
The brothers attended Cambridge Rindge and Latin High School, a public school that counts actors Matt Damon and Ben Affleck among its alumni but has a diverse student body that includes working-class immigrants from around the world.
The younger Tsarnaev brother, Dzhokhar, adjusted much more successfully to life in Massachusetts than Tamerlan. Friends describe him as a mild-mannered pot-smoker, and seem genuinely shocked that he could have been involved in violence.
Dzhokar made friends easily in high school and at the University of Massachusetts at Dartmouth, where fellow students knew him as relaxed, funny, and always up for a game of soccer.
The Twitter feed Dzhokhar's friends have identified as his chronicles a typical, restless teenage life. He's always hungry. He dreams of cheeseburgers. He's not fond of MTV or celery or homework. He jokes with friends about getting high, finding girls, watching the fantasy saga "Game of Thrones" on TV.
In a few tweets, he talks about his roots. Last March, for instance, he used the hashtag #chechnyanpower and then wrote: "a decade in America already, I want out".
A few posts from recent months offer hints of anger. In February, he posted: "Do I look like that much of a softy ... little do these dogs know they're barking at a lion." And in March: "Never underestimate the rebel with a cause."
But mostly, his tweets paint a picture of a laid back college student, with few hints of alienation or anger.
The day after the bombing, he, now notoriously, tweeted: "I'm a stress-free kind of guy." So at ease was he after the attacks that he went to the gym the following night, where he struck up a conversation about it with fellow student Zach Bettencourt.
"This is easy to do," Dzhokhar Tsarnaev said of the bombing, according to Bettencourt who spoke to Reuters. "These tragedies happen all the time in Afghanistan and Iraq."
Several of his friends have launched Facebook and Twitter campaigns proclaiming his innocence and arguing that he was set up. Others have said they believe so strongly in his good character that they would testify for him at trial.
SERIOUSLY MESSING AROUND
Dzhokhar may have been influenced by his charismatic older brother. A video posted on the Internet by the younger Tsarnaev with the caption "My brother, seriously messing around" shows Tamerlan as a mesmerizing goofball, sending up Chechens, Dagestanis and other ex-Soviet minorities with comedy accents in Russian, while the cameraman, presumably Dzhokhar, laughs wildly in admiration.
But it was the charming older Tsarnaev brother who seemed to have a harder time fitting in.
Through high school, and for years afterward, Luis Vasquez thought of his classmate Tamerlan Tsarnaev as "a big, friendly giant", who never lost the accent in his slow, deep voice.
Vasquez first noticed Tsarnaev in the halls of Cambridge Rindge and Latin High School because he always seemed to be just a few steps behind a vivacious group of girls that included Vasquez's girlfriend. Tamerlan was keeping tabs on his younger sister, Bella, Vasquez soon realized.
"If she was in the hallway somewhere, you knew he wasn't too far behind," Vasquez said. "He kept an eye on her, literally."
Bella was a free spirit who "wanted to partake fully in our American society" and thought "it's OK to flirt sometimes", Vasquez said. Tamerlan, however, made it clear that it wasn't OK - not in a menacing way, Vasquez said, but in a "big brother watching little sister kind of way".
"It was an honor thing. He was trying to keep her out of trouble," he said. Bella could not be reached for comment.
Though a bit reserved, Tamerlan was also approachable and friendly, Vasquez said. They stayed in touch for years after high school, bumping into each other in the supermarket, outside the boxing gym or on the Cambridge streets. Vasquez was always struck at how much his friend seemed to want to connect.
"He would look you in the eyes, ask you what was going on with your life," Vasquez said. "He was always leaning in, listening. His respect for other people was a little higher than most have," Vasquez said. "He would care."
The morning after Tamerlan was killed in the shootout, news reports seized on a quote from a caption in a photo essay that showed him training for boxing at a gym, in which he said he had no American friends because no one there understood him.
Vasquez said the quote has been misinterpreted: Tamerlan may have preferred the company of other immigrants and minorities to white, native-born Americans, but he was no loner.
The pictures clearly show him as a cocky, sociable young athlete, confident of his sporting skills, dressing in smart clothes and play-boxing with an attractive blonde woman. He was planning to represent New England at a national competition.
Tsarnaev was a bit arrogant when it came to his boxing, "but what athlete isn't cocky?" Vasquez said. "He knew he was good. He was good. So that's OK. No one's going to challenge that."
But about three years ago, Tsnarnaev abruptly dropped off the scene. He removed his Facebook page. Vasquez no longer saw him around the streets.
"He kind of disconnected himself," Vasquez said. He asked mutual friends if they had seen Tsarnaev, if they knew what he was up to. Some said they had heard he went back to Russia. But no one had details. No one knew he had married or had a child.
NOT WHAT YOU'D THINK OF AS NORMAL
The American dream never arrived for Tamerlan Tsarnaev. His boxing career didn't work out, nor did his studies at junior college. He was briefly detained by police when a girlfriend complained of violence, but the accusations were dropped.
He married Katherine Russell, a student at Suffolk University from a middle-class Rhode Island background, the daughter of a doctor and a nurse.
Katherine converted to Islam and left university without graduating. They had a daughter, Zahara, now 3. Tamerlan seems never to have found a full-time career. His family members say his new wife supported him, while he stayed home with the child.
Mary Silberman, whose apartment backs up to the rooms Tamerlan Tsarnaev rented, said she often heard loud arguments late at night - a woman's voice, mostly, yelling at a man.
"It wasn't enough to call the police," Silberman said. "It didn't sound like anyone was in physical danger." Yet the shouting, erupting at 11 p.m. or midnight, was loud enough to keep her up.
Silberman also heard the couple's young daughter crying frequently at night, the wails so sharp that she wondered why the mother wasn't responding. As the girl grew into a toddler, Silberman would see her sometimes staring out the window.
Their bedroom window had no proper curtains, just two mismatched sheets hung haphazardly to block the light. Plastic bags were stuffed in the sides of the window, apparently to keep out the cold.
"It wasn't what you would think of as normal," Silberman said. The family made her so uncomfortable, she said, that she made sure she pulled her chair out of view of their windows when she sat on her back deck.
The Russell family issued a statement the morning after the shootout saying they realized they had never really known Tamerlan Tsarnaev. The family home in leafy North Kingston Rhode Island is on the market for $467,000, and police cars now patrol the street. Katherine Russell did not respond to requests for comment via her lawyer.
Trouble integrating into new communities is an issue for all immigrants. In the case of Chechens who reached the West after the wars of the 1990s, such problems appear to be particularly acute for men who arrived as young adults, said author Oliver Bullough, who has spent years researching the Chechen diaspora.
Chechen culture encourages male bravado, something that has helped Chechens keep their identity through generations of oppression in Russia but which may make some Chechen men particularly prone to feelings of alienation.
"A Chechen man has, I think, a higher sense of self-worth than the average other man in Russia. It's a proud culture. And being in a situation where you are one of life's losers is particularly hard," said Bullough.
Tamerlan returned to Dagestan in 2012, where his mother and father had relocated after splitting up. Family members there who had not seen him for years were surprised by his new interest in religion.
His mother now speaks proudly of his apparent religious awakening, and says she does not believe he would have been capable of the Boston attacks.
"He changed when he started practicing Islam. He would read all the time," she said. "He had started going to nightclubs, but ever since I said to him that 'You are a Muslim, you should not do such things, they are haram', he became more religious," she told Reuters in English in Makhachkala.
During his stay in Dagestan, relatives say, he clearly stood out as an American, speaking Russian with a foreign accent and slipping into English when he could not remember a word.
"I don't think he was interested in friendships," his mother said, adding that he followed lessons online in the Koran to try and understand it in its original Arabic. "He was reading, always in front of the computer - he was taking classes on the Koran," she said.
"He was very interested. He didn't want to read it in translation. He said, 'Mama it's very difficult, but I want to do this'. He really wanted to get into the true reading of the Koran," she said. "I was happy about that."
Like other Chechens, the Tsarnaev brothers would have been steeped in the history of their people, including the two wars waged by Russian forces in Chechnya during their childhood in the 1990s, in which tens of thousands of civilians were killed.
As children, they never lived in the war zone itself: they attended a school in Makhachkala in neighboring Dagestan, a scruffy provincial capital 250 km (160 miles) from the Chechen frontier.
Now, when Tamerlan returned to Dagestan a decade after Russian President Vladimir Putin had crushed the separatist movement in Chechnya, a smaller Islamist insurgency had shifted from Chechnya to Dagestan itself. He would arrive in a city far more religious than the one he had left, and also more violent.
Veils and enveloping Islamic dress are increasingly replacing mini-skirts and high heels. Few cafes or stores now sell alcohol, fearing attacks by militants from an energized sect of strict Islamists known as Salafists, who have their own media outlets, charities and even a soccer club. Shootings and bombings are daily occurrences.
"No one is talking about the Boston bombing because such things happen every day here," said Renat, 36.
"I was taking the bus home from work about a month ago and boom! I don't know if it was a sniper, but the policeman standing at that crossroads there just crumpled," he said pointing to a traffic light.
In the past decade, Islam in Dagestan has been polarized between the Salafist school of orthodox Sunni Islam - which the authorities consider an alien import to the region - and the officially tolerated Sufi school, the traditional form of Islam in the Caucasus for centuries but which rebels now denounce.
The failures of the Russian state - police brutality, corruption, joblessness - have turned youths from the Kremlin-backed mainstream clerics into the embrace of puritanical Islam.
Sufi clerics have been killed by Salafist attackers. Young Salafists, whose ideas chime with those of puritan radicals in the Middle East, have been rounded up and, say rights activists, tortured by the police.
Tamerlan's trail on social media sites and in Russian-language videos posted on YouTube shows that he had taken sides in the dispute. Among his five favorite videos on YouTube is one that denounces Dagestan's traditional Sufi Muslims as heretical idol worshippers.
The young man who posted that video, but did not create it, told Reuters the sentiment it expressed was typical of the region's Salafists, who see themselves as part of a religious war: "His videos are pretty typical of Muslim youths here today: We are against the Sufis, they are against us. There is nothing strange in that," said the man, as he scrolled through Tamerlan's YouTube account in a Makhachkala Internet cafe.
He did not want to be identified for fear of the police.
GOING INTO THE FOREST
Youths from Dagestani villages who join the insurgency are said to "go into the forest". It is not clear if Tamerlan ever went to join them, although some in the region dismiss the prospect as highly unlikely on the grounds that fighters would have been reluctant to trust a man just off a plane from Boston.
U.S. officials have said Russian security services asked the FBI about Tamerlan in early 2011 out of concern he had embraced radical Islam and was going to travel to Russia to join underground groups. FBI agents interviewed him in Massachusetts in 2011 but found no serious reason for alarm. U.S. officials say that the FBI later asked Russia's Federal Security Service (FSB) for more information about him but did not receive any.
A Russian security source said Russia's secret police were tracking Tamerlan's movements while he was in Dagestan, but did not consider him "a high risk, just a point of interest".
He seems to have returned to the United States with firm views about Islam, unafraid to challenge authority figures for being insufficiently pious.
Since around the time he returned to Massachusetts he began attending services at the Islamic Society of Boston mosque in Cambridge. He made frequent appearances at Friday afternoon prayer, at times arriving before sunrise - sometimes with his younger brother in tow - for dawn services, said Anwar Kazmi, a member of the mosque's board of trustees.
Members of the congregation vividly remember Tamerlan interrupting the Friday sermon three months ago before the weekend of the U.S. national holiday marking the birthday of civil rights leader Martin Luther King, a Christian preacher.
The imam urged the congregation to learn from the examples of both King and the Prophet Mohammad. Apparently outraged by the comparison between the prophet and a non-Muslim, Tamerlan stood up and shouted "kafir" - infidel - at the imam. He then called the imam a "munafiq", or hypocrite, Kazmi said.
The congregation, several hundred strong, responded by shouting at Tamerlan to leave if he didn't like the sermon, Kazmi said.
Afterward, elders sat down with Tamerlan and explained that he had committed a serious breach of etiquette with his outburst. "He seemed to understand," Kazmi said - and continued to worship at the mosque, never again expressing such rage.
That outburst surprised some in the congregation because Tamerlan had previously been seen as an easy-going, inoffensive member of the community.
He had also gone out of his way to find one particular man and apologize for a slight he remembered his father committing years earlier, Kazmi said. His father, a part-time mechanic, had taken in the man's car to repair but delayed the job for weeks. Tamerlan found the man and personally apologized for that delay.
More recently, in the last few months, Tamerlan came across the same man stranded on the side of the road, his car having run out of fuel. He immediately offered to help, fetching a canister from his apartment, filling it at a station and returning to the stranded motorist to get him on his way again.
Kazmi said he could not mesh that portrait of a helpful neighbor with the picture of a ruthless killer that has emerged in recent days: "How do you reconcile the two?" Kamzi mused."That's what everyone is trying to answer."