Russian security services killed Abu Dujana in December during an assault on an apartment in Makhachkala, the capital of Dagestan. He led a small militant group in Dagestan that had links to Imarat Kavkaz.
While Tsarnaev was in Russia in 2012, he spent some of his time in Makhachkala, where his father lives today. U.S. officials told CNN analyst Tom Fuentes on Sunday they have found no further connection between Tsarnaev and Abu Dujana, but the investigation into his activities overseas continues.
September 5, 2012
Tsarnaev presents an application for U.S. citizenship, according to The New York Times. The application prompted "additional investigation" of him in 2013 by federal law enforcement agencies, officials told the newspaper. The officials declined to say how far that examination had progressed or what it covered, the Times said.
November 16, 2012
When a preacher at the Islamic Society of Boston Cambridge mosque says that it is appropriate to celebrate U.S. national holidays such as July 4 and Thanksgiving, Tsarnaev stands up and challenges him, arguing that celebrating holidays is "not allowed in the faith," the Islamic Society of Boston said. After the sermon, Tsarnaev repeatedly argues his viewpoint with the preacher, then leaves.
January 18, 2013
When a preacher at the same mosque says slain civil rights leader Martin Luther King Jr. was a great person, Tsarnaev stands up, shouts and calls him a "non-believer," the Islamic Society of Boston said. Tsarnaev accuses the preacher of "contaminating people's mind" and calls him a hypocrite. People in the congregation shout back at Tsarnaev, telling him to "leave now." Leaders of the mosque later tell him he will no longer be welcome if he continues to interrupt sermons. At future prayers, he is quiet.
April 15, 2013
Two explosions go off near the finish line at the Boston Marathon, killing three people and injuring more than 170. Authorities describe the blasts as a terrorist attack and vow to bring whoever is responsible to justice.
April 18, 2013
5 p.m.: The FBI releases photos and videos showing two men they describe as suspects in the Boston Marathon bombings.
11 p.m.: Police respond to a call on the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, has been shot. He dies from his injuries. Police later say they believe the bombing suspects were responsible for the shooting.
April 19, 2013
Tsarnaev dies after a shootout with police in Watertown, Massachusetts. Hours later, investigators reveal that he and his 19-year-old younger brother are the marathon bombing suspects.