The cocksure fighter, a flamboyant dresser partial to white fur and snakeskin, had been looking forward to redeeming the loss he suffered the previous year in the first round, when the judges awarded his opponent the decision, drawing boos from spectators who considered Tsarnaev dominant.
From one year to the next, though, the tournament rules had changed, disqualifying legal permanent residents - not only Tsarnaev, who was Soviet-born of Chechen and Dagestani heritage, but several other New England contenders, too. His aspirations frustrated, he dropped out of boxing competition entirely, and his life veered in a completely different direction.
Tsarnaev portrayed his quitting as a reflection of the sport's incompatibility with his growing devotion to Islam. But as dozens of interviews with friends, acquaintances and relatives from Cambridge to Dagestan showed, that devotion, and the suspected radicalization that accompanied it, was a path he followed most avidly only after his more secular dreams were dashed in 2010 and he was left adrift.
His trajectory eventually led the frustrated athlete and his loyal younger brother, Dzhokhar, to bomb one of the most famous athletic events in this country, killing three people and wounding more than 200 at the Boston Marathon, the authorities say. They say it led Tsarnaev, his application for citizenship stalled, and his brother, a new citizen and a seemingly well-adjusted college student, to attack their American hometown on Patriots' Day, April 15.
Tsarnaev now lies in the state medical examiner's office, his body riddled with bullets after a confrontation with the police four days after the bombings. He left behind an American-born wife who had converted to Islam, a 3-year-old daughter with curly hair, a 19-year-old brother charged with using a weapon of mass destruction, and a puzzle: Why did these two young men seemingly turn on the country that had granted them asylum?
Examining their lives for clues, the authorities have focused on Tsarnaev's six-month trip to the Russian republics of Chechnya and Dagestan, last year. But in Cambridge, sitting on the front steps of the ramshackle, brown-shingled house where the Tsarnaev family lived for a decade, their 79-year-old landlady urged a longer lens.
"He certainly wasn't radicalized in Dagestan," the landlady, Joanna Herlihy, said.
Herlihy, who speaks Russian and was friends with the Tsarnaevs, said she told law enforcement officials that his trip clearly merited scrutiny, but she said that Tsarnaev's embrace of Islam had grown more intense before that.
As his religious identification grew fiercer, Tsarnaev seemed to abandon his once avid pursuit of the American dream. He dropped out of community college and lost interest not just in boxing but also in music; he used to play piano and violin, classical music and rap, and his email address was a clue to how he once saw himself: The(USCORE)Professor(AT)real-hiphop.com. He worked only sporadically, sometimes as a pizza deliverer, and he grew first a close-cropped beard and then a flowing one.
He seemed isolated, too. Since his return from Dagestan, his wife and his child were the only Tsarnaevs living full time in the three-bedroom apartment on Herlihy's third floor.
Tsarnaev's two younger sisters had long since married and moved out; his parents, now separated, had returned to Dagestan, his mother soon after a felony arrest on shoplifting charges; and his brother had left for the University of Massachusetts at Dartmouth, returning home only on the occasional weekend, as he did recently after damaging his 1999 green Honda Civic by texting while driving.
"When Dzhokhar used to come home on Friday night from the dormitory, Tamerlan used to hug him and kiss him - hold him, like, because he was a big, big boy, Tamerlan," their mother, Zubeidat, 45, said last week, adding that her older son had been "handsome like Hercules."
Not long after he gave up his boxing career, Tsarnaev married Katherine Russell of Rhode Island in a brief Islamic ceremony at a Dorchester mosque in June 2010. She has declined to speak publicly since the attacks.
His wife primarily supported the family through her job as a home health aide, scraping together about $1,200 a month to pay the rent. While she worked, Tsarnaev looked after their daughter, Zahira, who was learning to ride the tricycle still parked beside the house, neighbors said. The family's income was supplemented by public assistance and food stamps from September 2011 to November 2012, state officials said.
It was probably not the life that Anzor Tsarnaev had imagined for his oldest child, who, even as a boy, before he developed the broad-shouldered physique that his mother described as "a masterpiece," dreamed of becoming a famous boxer.
But then the father's life had not gone as planned either. Once an official in the prosecutor's office in Kyrgyzstan, he had been reduced to working as an unlicensed mechanic in the back lot of a rug store in Cambridge.
"He was out there in the snow and cold, freezing his hands to do this work on people's cars," said Chris Walter, owner of the store, Yayla Tribal Rug, "I did not charge him for the space because he was a poor, struggling guy with a good heart."
Tamerlan Tsarnaev was born on Oct. 21, 1986, five years before the dissolution of the Soviet Union, in Kalmykia, a barren stretch of Russian territory by the Caspian Sea.
A photograph of him as a baby shows a cherubic child wearing a knit cap with a pom-pom, perched on the lap of his unsmiling mother, who has spiky black bangs and an artful pile of hair. She did not cover her head then, as she does now; she began wearing a hijab only a few years ago, in the United States, prodded by her son just as she was prodding him, too, to deepen his faith.
When he was still little, his parents moved from Kalmykia to Kyrgyzstan, a former Soviet republic, where their other three children were born. They left there during the economic crisis of the late 1990s and spent a few brief months in Chechnya, then fled before the full-scale Russian military invasion in 1999. They sought shelter next in his mother's native Dagestan.
In an interview there, Patimat Suleimanova, her sister-in-law, said the family had repeatedly been on the run from war and hardship in those days: "In search of peace, they kept moving," she said.
Finally, Anzor Tsarnaev sought political asylum in the United States. He arrived first, with his younger son, in the spring of 2002. His older son, a young man of 16, followed with the rest of the family in July 2003.
Their neighborhood in Cambridge was run-down then, with car repair lots where condominiums have since arisen, but the city has long been especially welcoming to immigrants and refugees; its high school has students from 75 countries.
The schools superintendent, Jeffrey Young, described Cambridge as "beyond tolerant."
"How is it that someone could grow up in a place like this and end up in a place like that?" he said of the Tsarnaevs.
Unlike his little brother, who was well integrated into the community by the time he started high school, Tsarnaev was a genuine newcomer when he entered the Cambridge Rindge and Latin School, from which he graduated in 2006. Enrolled in the large English as a Second Language program, he made friends mostly with other international students and his demeanor was reserved, one former classmate, Luis Vasquez, said.
"The view on him was that he was a boxer and you would not want to mess with him," said Vasquez, now 25 and a candidate for the Cambridge City Council. "He told me that he wanted to represent the U.S. in boxing. He wanted to do the Olympics and then turn pro."
Jumping right into boxing after his arrival in the United States, he called attention to himself immediately in more ways than one. During registration for a tournament in Lowell, he sat down at a piano and lost himself for 20 minutes in a piece of classical music. The impromptu performance, so out of place in that world, finished to a burst of applause from surprised onlookers.
"He just walked over from the line and started playing like he was in the Boston Pops," his trainer at the time, Gene McCarthy, 77, recalled.
Having trained in Dagestan, where sport fighting has an impassioned following, Tsarnaev boxed straight-legged like a European and not crouched, American-style. He also incorporated showy gymnastics into his training and fighting, walking on his hands, falling into splits, tumbling into corners. So as he started working out in Boston-area clubs - and winning novice tournament fights - he made an impression, although not an entirely positive one.
"For a big man, he was very agile," said Tom Lee, president of the South Boston Boxing Club.
"He moved like a gazelle and was strong like a horse. He was a big puncher. But he was an underachiever because he did not dedicate himself to the proper training regimen."
In 2009, Tsarnaev won the New England Golden Gloves championship in the 201-pound division, which qualified him for the national tournament in Salt Lake City in May. Introducing what would become his signature style, he showed up overdressed, wearing a white silk scarf, black leather pants and mirrored sunglasses while the other contenders wore sweatsuits.
Stepping into the ring, as The Lowell Sun described it, Tsarnaev floored Lamar Fenner of Chicago with an explosive punch that required an eight-count from the referee, and then he seemed to control the rest of the fight.
Bob Russo, then the coach of the New England team, said: "We thought he won. The crowd thought he won. But he didn't."
Fenner's mother, Marsha, said her son had called her the night of his "bout with the bomber," thrilled to have defeated an opponent he described as unnervingly strong. Her son, who died of heart problems last year at 29, ended up coming in second in the tournament and turning professional, she said.
If Tsarnaev was chastened by the defeat, it did not temper his behavior. During a preliminary round of the New England Golden Gloves in 2010, in a breach of boxing etiquette, he entered the locker room to taunt not only the fighter he was about to face but also the fighter's trainer.
Wearing a cowboy hat and alligator-skin cowboy boots, he gave the two men a disdainful once-over and said: "You're nothing. I'm taking you down."
The trainer, Hector Torres, was furious and subsequently lodged a complaint, arguing that
Tsarnaev should not be allowed to participate in the competition because he was not a citizen.
As it happened, Golden Gloves of America was just then changing its policy. It used to permit legal immigrants to compete in its national tournament three out of every four years, barring them only during Olympic qualifying years, James Beasley, the executive director, said. It decided in 2010, however, that the policy was confusing and moved to end all participation by noncitizens in the Tournament of Champions.
So Tsarnaev, New England heavyweight champion for the second year in a row, was stymied. The immigrant champions in three other weight classes in New England were blocked from advancing, too, Russo said.
Tsarnaev was devastated. He was not getting any younger, and he was more than a year away from being even eligible to apply for U.S. citizenship, and there appeared to be a potential obstacle in his path.
In the summer of 2009, Tsarnaev was arrested after a report of domestic violence.
His girlfriend at the time had called 911, "hysterically crying," to say he had beaten her up, according to the Cambridge police report. Tsarnaev told the officers that he had slapped her face because she had been yelling at him about "another girl."
Eventually, charges against him would be dismissed, the records show, so the episode would not have endangered his eventual citizenship application.
His life was changing, though. He married. He had a child. And he largely withdrew from Cambridge social life and from many of the friendships he had enjoyed. "He had liked to party," said Elmirza Khozhugov, 26, his former brother-in-law, who lost touch with him in 2010, "but there was always the sense that he felt a little guilty that he was having too much fun, maybe."
In 2011, the Russian security service cautioned the FBI, and later the CIA, that "since 2010" Tsarnaev had "changed drastically," becoming "a follower of radical Islam." The Russians said he was planning a trip to his former homeland to connect with underground militant groups.
An FBI investigation turned up no ties to extremists, the bureau has said.
In early 2012, Tsarnaev left his wife and child for a six-month visit to Russia. His parents, speaking in Dagestan, portrayed it as an innocuous visit to reconnect with family and to replace his nearly expired passport from the Republic of Kyrgyzstan with a Russian one. His father said he had kept his son close by his side as they visited relatives, including in Chechnya, and renovated a storefront to turn it into a perfume shop.
But U.S. officials say Tsarnaev arrived in Russia months before his father returned to Dagestan and so did not have the continuous tight supervision, as described by his father.
Also, Tsarnaev, with no apparent sense of urgency about his travel documents, waited months to apply for a Russian passport, and returned to the United States before the passport was ready for him.
After his return, Tsarnaev applied for U.S. citizenship, a year after he was eligible to do so; but the FBI investigation, though closed, had caused his application to be stalled. Underscoring how detached he had become, he no longer had any valid passport or international travel document, and Cambridge, to which he had a hard time readapting, was now his de facto home more than ever.
He grew a 5-inch beard, which he shaved off before the bombings, and interrupted prayers at his mosque on two occasions with outbursts denouncing the idea that Muslims should observe U.S. secular holidays. He engaged neighbors in affable conversations about skiing one week and heated ones about U.S. imperialism the next.
At a neighborhood pizzeria, wearing a head covering that matched his jacket, he explained to Albrecht Ammon, 18, that "the Quran is great and flawless, and the Bible is ripped off from
the Quran, and the U.S. used the Bible as an excuse to invade different countries."
"I asked him about radical Muslims that blow themselves up and say, 'It's for Allah,"' Ammon said. "He said he wasn't one of those Muslims."