Sean Allen Collier, 26, was an MIT police officer killed in the line of duty on the night of April 18, 2013. While seated in his patrol car on the Cambridge campus, he was ambushed and shot multiple times. The attack came hours after FBI images of the Boston Marathon bombing suspects were released; brothers Dzhokhar and Tamerlan Tsarnaev approached Collier’s vehicle and opened fire at close range. Investigators report the shooting followed an apparent attempt to remove his service weapon, which could not be taken from its triple-retention holster.

Collier had joined the MIT Police in January 2012 and was noted for his engagement with students and commitment to the community. His murder dramatically escalated the manhunt for the bombing suspects, which led to a carjacking, a shootout in Watertown in which Tamerlan Tsarnaev was killed, and the later capture of Dzhokhar Tsarnaev hiding in a boat in a Watertown backyard. Collier is commemorated by a permanent memorial on the MIT campus.