Dzhokar Tsarnaev, 19, the Boston Marathon attack suspect now at large, came to the United States on July 1, 2002, at age 8 on a tourist visa, a federal source said. While here, he sought asylum and became a citizen on September 11, 2012.
His older brother Tamerlan Tsarnaev, who was killed in a shootout with police overnight, came to the United States four years after his brother, on September 6, 2006, at the age of 20, the source said. He came legally but was not naturalized. He was a green card holder and in the country lawfully.
[Updated 1:23 p.m. ET]
Dzhokar Tsarnaev became a U.S. citizen on September 11, 2012, a federal official said Friday.
[Updated 1:17 p.m. ET]
Here's the latest chronology that CNN has on Thursday night's shooting and subsequent manhunt:
The violence began late Thursday with the robbery of a convenience store, according to Timothy Alben, superintendent of the Massachusetts state police. Soon after, in Cambridge, across the Charles River from Boston, Massachusetts Institute of Technology police officer Sean Collier was fatally shot while he sat in his car, the Suffolk County District Attorney's Office said in a statement.
Police believe the Boston Marathon bombing suspects were responsible for the shooting.
The two suspects, according to authorities, then hijacked a vehicle at gunpoint in Cambridge, telling the driver that they were the marathon bombers, a law enforcement source told CNN's Joe Johns. At some point, apparently at a gas station, the source said, the driver escaped.
Police, who were tracking the vehicle using its built-in GPS system, picked up the chase in Watertown. The pursuit went into a residential neighborhood, with the suspects throwing explosives at the police. A firefight erupted and ultimately one suspect -- later identified as Tamerlan Tsarnaev -- got out of the car. Police shot him, and his brother ran over him as he drove away, according to the source.
A source briefed on the investigation said Tamerlan Tsarnaev was wearing explosives and an explosive trigger. He died later at Beth Israel Hospital.
Richard H. Donohue Jr., 33, a three-year veteran of the transit system police force, was shot and wounded in the incident and taken to a hospital, a transit police spokesman said Friday. The officer's condition was not immediately known.
[Updated 12:45 p.m. ET]
Police are continuing to run down new leads and go door to door in Watertown in the Boston Marathon terror attack investigation, said Timothy Alben, superintendent of the Massachusetts state police. He told reporters that law enforcement will conduct a controlled blast later in Cambridge, an indication that police found suspected explosives.
[Updated 12:44 p.m. ET]
Massachusetts Gov. Deval Patrick says his request for people in the Boston area to stay indoors remains in effect for now. "We know what an inconvenience it is, in Watertown and Cambridge in particular ... but it's been enormously helpful ... to law enforcement."
[Updated 12:30 p.m. ET]
The Kyrgyz government said Friday that the two Boston Marathon bombing suspects moved from Kyrgyzstan 12 years ago to the Russian region of Dagestan, from where the Tsarnaev family immigrated to the United States.
"Given that the suspects left the Republic at the ages of 8 and 15, the State Committee for National Security of Kyrgyzstan considers it inappropriate to link them to Kyrgyzstan," it said.
[Updated 12:25 p.m. ET]
Dzhokar Tsarnaev, 19, was registered at the University of Massachusetts-Dartmouth, which ordered its campus evacuated Friday. The school is 65 miles south of Cambridge, just west of New Bedford.
"UMass Dartmouth has learned that a person being sought in connection with the Boston Marathon bombing has been identified as a student registered at UMass Dartmouth," the school said in a news release. "The campus is closed. Individuals on campus should shelter in place unless instructed otherwise."
[Updated 12:06 p.m. ET]
Boston bombing suspect Dzhokar Tsarnaev has tweeted since the Boston Marathon bombings on what friends of his tell CNN is his Twitter account.
The tweets included one at 1:43 a.m. Wednesday that said, "I'm a stress free kind of guy."