This combination of photos provided on Friday, April 19, 2013 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 Photo/FBI, BRIC)
This surveillance photo released via Twitter Friday, April 19, 2013 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 Photo/Boston Police Department)
Officials brief the media on a standoff in Watertown, Mass., early Friday. Authorities say one of two suspects in the Boston Marathon bombing is dead and a massive manhunt is underway for another in the Boston suburb of Watertown early Friday morning.
This photo released by the FBI early Friday April 19, 2013, 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 Photo/FBI)
This photo released Friday, April 19, 2013 by the Federal Bureau of Investigation shows a suspect that officials identified as Dzhokhar Tsarnaev, being sought by police in the Boston Marathon bombings Monday. (AP Photo/Federal Bureau of Investigation)
This wanted poster was released by the FBI on Friday, April 19, 2013, showing Dzhokhar Tsarnaev, the suspect the FBI orginally called suspect number 2 in the bombings at the Boston Marathon. (AP Photo/FBI)