Boston Marathon bombing suspects

AP/The Lowell Sun/Julia Malakie, Bkontakte

Brothers Tamerlan Tsarnaev, 26, left, and Dzhokhar A. Tsarnaev, 19, right, were identified as the suspects in the Boston Marathon bombings that killed three people and wounded more than 180 others on April 15, 2013. On April 19, 2013, The FBI released photos and videos of the two young men, who were seen carrying backpacks as they mingled among revelers at the marathon, to enlist the public's help finding the suspects. A few hours later, the brothers engaged in a long night of violence that included killing an MIT police officer on campus in Cambridge, Mass., then stealing a car at gunpoint, injuring a transit officer in a firefight and throwing explosive devices at police during their getaway attempt, authorities said. Tamerlan Tsarnaev, 26, died during the gunfire exchange and Dzhokhar Tsarnaev remains at large.

In a photo released by the FBI, Tamerlan Tsarnaev, left, and Dzhokhar Tsarnaev are seen at the Boston Marathon on April 19, 2013, prior to the bombing.

Dzhokar Tsarnaev, 19, who was previously identified as Suspect #2 in the Boston Marathon bombing investigation, is still at large April 19, 2013.

Tamerlan Tsarnaev in a Feb. 17, 2010 photo. Tamerlan Tsarnaev, 26, who had been known to the FBI as Suspect No. 1 in the Boston Marathon Explosions and was seen in surveillance footage in a black baseball cap, was killed overnight on Friday, April 19, 2013, officials said.

An undated picture the of the 19-year-old Dzhokhar Tsarnaev posted on his VKontakte page, a Russian social media site.

AP Photo/Boston Regional Intelligence Center

Dzhokhar Tsarnaev, identified by the FBI as Suspect #2 in the Boston Marathon bombings.

Dzhokhar A. Tsarnaev, left, and Here & Now host Robin Young's nephew, right, pose for a photo after graduating from Cambridge Rindge and Latin High School in Cambridge, Mass. Tsarnaev has been identified as the surviving suspect in the marathon bombings. Two suspects in the Boston Marathon bombing killed an MIT police officer, injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left one of them dead and another still at large Friday, April 19, 2013.

Surveillance photo of Dzhokhar Tsarnaev, identified by the FBI as Suspect #2 in the Boston Marathon bombings.

Suspect #1 (left) and Suspect #2 at the Boston Marathon on April 15, 2013.

Suspect #2 at the Boston Marathon on April 15, 2013.

Suspect #2 at the Boston Marathon on April 15, 2013.

Suspect #1 (right) and Suspect #2 at the Boston Marathon on April 15, 2013.