Profile: Dzhokhar and Tamerlan Tsarnaev
Information is emerging about the lives of brothers Dzhokhar and Tamerlan Tsarnaev, who are suspected of bombing the Boston Marathon.
Tamerlan, 26, died during a shootout with police on 18 April. His 19-year-old brother, Dzhokhar, was captured a day later, found hiding in a boat in the backyard of a house in Watertown, a suburb of Boston.
The brothers lived in the Massachusetts town of Cambridge, home of the prestigious Harvard University. The family emigrated to the US in 2002.
There has been mixed information about the route they took to get there. The Tsarnaevs are ethnic Chechens from the troubled Caucasus region of southern Russia. Chechnya is a predominantly Muslim area that has fought for full independence from Russia in the past.
They are thought to have lived in Kyrgyzstan, a Central Asian republic which is home to many Chechen refugees who were deported under Stalin. Dzhokhar was reportedly born there in 1994.
The family was eventually forced to flee to the neighbouring Russian republic of Dagestan after the Second Chechen War broke out in 1999.
Three years later, they made their way to the US.
The father, Anzor Tsarnaev, and Dzhokhar arrived in the US on a tourist visa in April 2002 and applied for political asylum, federal law enforcement officers told the New York Times.
Tamerlan is thought to have followed at a later stage.
Anzor Tsarnaev recently moved back to Dagestan after he and his wife divorced.
Mr Tsarnaev told the BBC he believed the secret services had framed his sons. He said Dzhokhar (pronounced Jo-kar) was a dedicated second-year medical student who hoped to become a brain surgeon some day.
Both brothers attended the Cambridge Rindge and Latin School.
Dzhokhar received a $2,500 (£1,600) scholarship awarded to promising local high school seniors wanting to pursue further education.
The teenager, who was also an all-star wrestler, went on to study at the University of Massachusetts.
He became an American citizen in 2012.
Dzhokhar's Facebook profile gives "Islam" as his world view and says his life goals are "career and money". Meanwhile, his page on Russian social networking site VKontakte showed he was a member of Chechen groups.
Recent entries on what is reported to be his Twitter feed - @J-tsar - include "I'm a stress free kind of guy" on 17 April and "There are people that know the truth but stay silent & there are people that speak the truth but we don't hear them cuz they're the minority", on 16 April.
There was nothing to suggest his involvement in the Boston bombings.
Many of his school friends expressed shock at the news, describing him as a popular teenager.
A different picture has begun to emerge of the elder brother as someone embittered toward the US, interested in radical Islam and influential over his younger brother.
The FBI interviewed Tamerlan in 2011 at the request of a foreign government over concerns that he may be a "follower of radical Islam". They dropped the investigation after finding no cause for concern.
But agents have now focused their attention on a trip Tamerlan made to Dagestan last year.
He spent much of his time there praying and learning to read the Koran, according to one of his aunts.
A gifted amateur boxer, Tamerlan had increasingly turned to Islam in recent years after experiencing problems with the law and some family issues.
Tamerlan had faced a trial in 2009 over slapping a girlfriend but the domestic abuse case was dismissed.
His mother told the Wall Street Journal she had encouraged her son's study of the Koran to keep him from getting into further trouble.
"I started reading and started learning, I started reading with my Tamerlan", she said.
In 2010, Tamerlan told a student-run magazine that he had stopped drinking and smoking - "God said no alcohol" - and expressed concern that there were "no values anymore".
"I don't have a single American friend. I don't understand them," he was quoted as saying by the Boston University publication.
The magazine had interviewed and photographed him in the gym where he used to work out.
He had reportedly taken a semester off from the Bunker Hill Community College in Boston to train for a big competition.
But soon after, Tamerlan dropped the sport because he believed it to be against his religion. He also married and had a daughter.
Russian news agency RIA Novosti says "extremist material" was on the YouTube account belonging to Tamerlan.
The BBC has been unable to confirm the information about material on the page.
"Several albums were posted, one of them titled 'Terrorist'. The album contains two video clips, which are inaccessible, because the account linked to them has been removed. Also on the playlist there are conversations about the religion of Fayz Mohammad, who is famous for his radical utterances," RIA Novosti said.
Meanwhile the brothers' uncle, Ruslan Tsarni, said the brothers had "put shame on our family and on the entire Chechen ethnicity".
He said he had last seen his nephews in December 2005.
There had never been any apparent sign of "hatred toward the US" or else he would have turned them over to the police himself, he added.
Asked what he thought provoked the bombings, the uncle said: "Being losers, hatred to those who were able to settle themselves.
"These are the only reasons I can imagine of. Anything else, anything else to do with religion, with Islam, it's a fraud, it's a fake."