Updated: April 19, 2013, 12:00 AM
In pictures: Drama as Boston police exchange fire with bombing suspects
epa03667992 Police search neighborhoods yard by yard after a police chase and shootout with two heavily armed men shortly following the shooting of an MIT police officer just three days after the dual bombings at the Boston Marathon in Watertown, Massachusetts, USA, 19 April 2013. Three people were killed and over 100 were injured when two bombs exploded on 15 April 2013 at the finish line of the marathon. EPA/MATT CAMPBELL *** Local Caption *** 03667992.jpg
Police with guns drawn search for a suspect in Watertown, Massachusetts. Earlier, a Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. Mario Tama/Getty Images/AFP
Colonel Timothy Albens (C), of the Massachusetts State Police, Boston Police Commissioner Ed Davis (L) and Watertown Chief of Police Edward P. Deveau (R) speak to the media as a search for the second of the two suspects wanted in the Boston Marathon bombi???
Police officers walk near a crime scene in Watertown, Mass, 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
Police officers aim their weapons in Watertown, Mass, 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
Police officers (not pictured) keep a man on the ground in Watertown, Massachusetts following the shooting of a police officer at the Massachusetts Institute of Technology (MIT) touching off a manhunt for suspects just days after the Boston Marathon bombi???
Heavy armed police officers arrive at the scene of a police manhunt in Watertown, Massachusetts following the shooting of a police officer at the Massachusetts Institute of Technology (MIT), April 19, 2013. REUTERS/Brian Snyder
A law enforcement vehicle carries a bomb disposal device through Watertown during a search for the two men suspected of setting off two explosions during the Boston Marathon in Watertown, Massachusetts, April 19, 2013. REUTERS/Lucas Jackson
Police officers aim their weapons 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. AP Photo/Matt Rourke
This surveillance photo released via Twitter Friday by the Boston Police Department shows a suspect entering a convenience store that police are pursuing in Watertown, Mass, April 19, 2013. AP Photo/Boston Police Department