The suspect who was captured alive late on April 19 after a massive manhunt was identified as 19-year-old Dzhokhar Tsarnaev.
Police launched the hunt for Tsarnaev after his 26-year-old brother, Tamerlan -- also a suspect in the bombing -- was killed earlier in the day in a shootout with police in Watertown, near Boston.
Biographic details on the Tsarnaevs are now beginning to emerge.
Tamerlan was born in Kyrgyzstan and Dzhokhar is thought to have been born in the southern Russian republic of Daghestan, according to some relatives and Kyrgyz officials interviewed by RFE/RL's Kyrgyz Service*.
According to Ruslan Tsarni, who identified himself to U.S. media as the boys' uncle, the family moved to the United States around 2003.
However, details of the men's status in the United States remain unclear.
Unnamed sources told CNN that Dzhokhar came to the United States as a tourist with his family before requesting asylum. A number of reports said he became a naturalized U.S. citizen in 2012.
A source told CNN that Tamerlan came to the United States several years later and was a green-card holder.
The information could not be independently verified.
Prior to moving to the United States, the family also spent time in the North Caucasus.
On what appears to be his vKontakte page, Dzhokhar Tsarnaev says he studied at School No. 1 in Makhachkala, Daghestan, sometime between 1999 and 2001.
The school principal, Temirmagomed Davydov, said that Dzhokhar attended first grade while his brother Tamerlan attended eighth grade at the time.
Yelena Bandurina, a spokeswoman for the school, told RFE/RL: “They studied one year at our school. There were also two sisters. They arrived from Kyrgyzstan and then moved to America.”
WATCH: An interview with the headmaster of the school in Makhachkala that the Tsarnaevs attended:
Dzhokhar was later enrolled at the Cambridge Rindge and Latin School in Massachusetts, winning a $2,500 scholarship in 2011 and captaining his high-school wrestling team as a senior.
He is currently enrolled as a student at the University of Massachusetts-Dartmouth.
Tamerlan, meanwhile, appears to have had Olympic boxing ambitions, training at a martial arts center in Boston and appearing in a photo essay by Johannes Hirn called "Will Box For Passport" and going on to represent New England in a 2009 national boxing competition in Utah.
That story quotes Tamerlan as saying that unless his native Chechnya becomes independent, he would rather compete for the United States than for Russia.
"I don't have a single American friend," he is quoted as saying. "I don't understand them."
Tamerlan studied at Bunker Hill Community College with aims of becoming an engineer. He had a wife and a young daughter.
Sources quoted in the U.S. media, including the brothers' aunt, say that Tamerlan, and perhaps Dzhokhar, had taken an increased interest in Islam in recent years.
An unnamed "family friend" quoted by "The Wall Street Journal" says Tamerlan dropped out of school and had become drawn into religion. The source says Dzhokhar had also devoted more attention to Islam recently.
Maret Tsarnaeva, the aunt, told AP that Tamerlan had started praying five times a day two years ago or so.
What appears to be Tamerlan's YouTube page lists links labeled "terrorists" and videos of Islamic teachings. In one video, singing is heard as bombs explode from high-rise buildings.
BACKGROUND: Analyst Liz Fuller's 2010 overview of websites linked with the North Caucasus insurgency
“The elder went to the mosque. The FBI often came to our home and asked about us, about our thoughts," Anzor Tsarnaev, the father of the two suspects, told RFE/RL's North Caucasus Service from Makhachkala. "The younger studied and was far away from all this. They just killed them. If anything had happened, they would not have killed them. They just needed to get rid of them."
Dzhokhar's vKontakte page lists his world view as "Islam," his personal priority as "career and money," and his languages as English, Russian, and Chechen.
It also has jokes: "A car's on the move. A Daghestani, a Chechen, and an Ingush are sitting in it. Question -- who's driving? Answer -- the police."
It also known that Tamerlan traveled out of the United States at least twice.
Turkish Interior Minister Muammer Guler said he spent 10 days in Turkey in 2003.
Law-enforcement officials told U.S. media that Tamerlan traveled to Russia from the United States in 2012 and returned six months later.
Meanwhile, those who knew the brothers in Cambridge are expressing shock.
George McMasters, the aquatics coordinator at Harvard University, hired Dzhokhar as a lifeguard several years ago.
"I knew he was from Russia. I had asked him where he was from, with his name, [but] he seemed like a regular, young American boy," McMasters told RFE/RL. "He did know that I had been in Iraq [as a military reservist] and I was going to Afghanistan, so he asked me a little bit about what the wars were like. I told him it was tough duty and a lot of sad things, but he never pressed me for any information on explosives or anything like that."
Samuel Gebru, one of Dzhokhar's schoolmates, told RFE/RL that he was "bright" and "happy" and "an active member of our community."
He said he hoped that observers would not rush to judge Dzhokhar before a complete investigation. He also said he hoped others would consider "the bigger picture."
"This incident does not define who we are as a people in Cambridge and worldwide, as a whole," Gebru said, "that there is more to Cambridge, there is more to Chechnya, there is more to Islam, there is more to immigration than this issue in particular."
*CORRECTION: This story previously quoted a Kyrgyz Interior Ministry source confirming that both Tsarnaev brothers were born in Kyrgyzstan. Other sources say that Tamerlan Tsarnaev, 26, was born in Tokmok, Kyrgyzstan, near the border with Kazakhstan, and 19-year-old Dzhokhar Tsarnaev was born in Daghestan.