Massachusetts Institute of Technology

WATERTOWN, MA - APRIL 19:  Police with guns drawn search for a suspect on April 19, 2013 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. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge. It's not clear whether the shootings are related or whether either are related to the Boston Marathon bombing.

Mario Tama/Getty

Police with guns drawn on Friday search for a suspect in Watertown, Massachusetts. A Massachusetts Institute of Technology campus police officer was shot and killed late on Thursday night at the school’s campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in Watertown, a city near Cambridge.