A man applauds as police leave the Watertown scene of the arrest of a suspect of the Boston Marathon bombings Friday night. (Charles Krupa/AP)A gathering of people applaud as first responders leave the scene after the arrest of a suspect of the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Charles Krupa)Two women applaud after the arrest of a suspect of the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Charles Krupa)This still frame from video shows Boston Marathon bombing suspect Dzhokhar Tsarnaev visible through an ambulance after he was captured in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Robert Ray)Police officers guarded the entrance to Franklin street where there was an active crime scene in the search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. (AP Photo/Matt Rourke)Police officers guard the entrance to Franklin street where there is an active crime scene search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013. (AP Photo/Matt Rourke)Law enforcement search for the suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case. (AP Photo/Matt Rourke)People gathered at Mt. Auburn St. at the corner of Chester St. a few streets away from Franklin St. late Friday afternoon after shots were fired in the area. Police have sealed off the area. (Kevin Sullivan/WBUR)A woman carries a girl from their home as a SWAT team searching for a suspect in the Boston Marathon bombings enters the building in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Charles Krupa)A SWAT team drives through a neighborhood while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Charles Krupa)A girl looks out the window of her family's home as a SWAT team drives through her neighborhood while searching for a suspect in the Boston Marathon bombings in Watertown, Mass., Friday, April 19, 2013. (AP Photo/Charles Krupa)A lone pedestrian walks along Pearl Street in downtown Boston Friday, April 19, 2013 after mass transit was suspended while a suspect was hunted following bombings near the finish line of the Boston Marathon Monday. (AP Photo/Bill Sikes)Police in tactical gear conduct a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. (AP Photo/Matt Rourke)Armed National Guard riding in the back of a armored truck moving down Nichols Ave. Friday April 19, 2013. (Jesse Costa/WBUR)Belmont Police racing down Belmont Street on the Watertown line. Friday April 19, 2013. (Jesse Costa/WBUR)National Guard set up caution tape across Nichols Ave. Friday April 19, 2013. (Jesse Costa/WBUR)Boston Special Operations and National Guard search the streets Nichols and Dexter Avenues. Friday April 19, 2013. (Jesse Costa/WBUR)An FBI agent goes door-to-door evacuating residents of Norfolk Street as investigators search for a suspect in the Boston Marathon bombings, in Cambridge, Mass., Friday, April 19, 2013.(AP Photo/Michael Dwyer)This locator map shows the location and time line of the suspects in the Boston Marathon explosions. Boston police say one of the two suspects in the Boston Marathon bombing is dead after the killing of an MIT police officer and a shootout with police. A massive manhunt is underway for the other. (AP Photo)A police officer evacuates a shoeless man holding a child as members of law enforcement continue to search for the bombing suspect in Watertown Friday morning. (Matt Rourke/AP)A police officer with is weapon drawn conducts a search for a suspect in the Boston Marathon bombings, Friday, April 19, 2013, in Watertown, Mass. (AP Photo/Matt Rourke)A message calling for citizens of Boston to "Shelter in Place" flashes on a sign on I-93 near the Zakim Bridge in Boston Friday, April 18, 2013. The Boston area was all but paralyzed as a manhunt continued for Dzhokhar Tsarnaev, one of the two suspects in the Boston Marathon bombing. (AP Photo/Elise Amendola)A sign along I-93 in Medford, Mass. announces no MBTA service Friday, April 19, 2013. (AP Photo/Elise Amendola)A deserted Commonwealth Ave. on Friday morning, April 19, 2013. (Will Smith/WBUR)MBTA transit police turn away a commuter at Malden Center station in Malden, Mass. Friday, April 18, 2013 as area MBTA commuter trains are suspended. (Elise Amendola/AP)