Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon ... more 
Police officers aim their weapons Friday, April 19, 2013, in Watertown, Mass. A tense night of police activity that left a university officer dead on campus just days after the Boston Marathon bombings and amid a hunt for two suspects caused officers to converge on a neighborhood outside Boston, where residents heard gunfire and explosions.(AP Photo/Matt Rourke) less 
1 / 30
Associated Press | Photo By Matt Rourke
Fri, Apr 19, 2013 4:47 AM EDT