FBI releases photos of suspects in the Boston Marathon bombing

April 19, 2013: This combination of photos provided by the Federal Bureau of Investigation, left, and the Boston Regional Intelligence Center, right, shows a suspect that officials have identified as Dzhokhar Tsarnaev, being sought by police in connection with Monday's Boston Marathon bombings. (AP)

April 19, 2013: This image provided by the Boston Regional Intelligence Center shows Dzhokhar A. Tsarnaev, identified by the FBI as suspect number 2, in the Boston Marathon bombings. (AP)

April 19, 2013: This surveillance photo released via Twitter by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass. Police say he is one of two suspects in the fatal shooting of an MIT police officer and tied to the Boston Marathon bombing. (AP)

This poster released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, wearing a black cap, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP/FBI)

This poster released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 2, wearing a white cap, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP2013)

This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, in black cap, behind the pink hat, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP2013)

This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, in black cap, center, walking ahead of suspect number 2, walking into frame at far top right with white hat, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP2013)

Suspects 1 and 2 seen walking down Boylston Street towards the finish line. (FBI)

Another image of both suspects seen on Boylston Street (FBI)

This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 2, bottom left, in white cap, walking through the crowd behind suspect number 1, not seen, in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP2013)

This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, black cap, center, walking in front of suspect number 2, not seen, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP/FBI)

This frame grab from a video released by the FBI on Thursday, April 18, 2013, shows what the FBI are calling suspect number 1, black cap with backpack at top center, walking in front of suspect number 2, white cap, through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI) (AP/FBI)

Image of Suspect #2 (FBI)

Suspect #2 seen here wearing a white baseball cap in the crowd. (FBI)

Suspect #1 seen  walking through crowd on Boylston Street (FBI)

April 19, 2013: This photo released by the FBI shows what the FBI is calling suspect number 2, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP/FBI)

(FBI)

(FBI)

April 19, 2013: This photo released by the FBI shows what the FBI is calling suspect number 1, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP Photo/FBI)

April 19, 2013: This photo released by the FBI shows what the FBI is calling the suspects together, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP/FBI)

April 19, 2013: This photo released by the FBI shows what the FBI is calling suspect number 2 behind a lady, walking through the crowd in Boston on Monday, April 15, 2013, before the explosions at the Boston Marathon. (AP./FBI)