(04/22/13-Cambridge,MA) MIT Police Chief John DiFava is hugged by a member of the MIT community, shortly after a moment of silence that commemorated the one week mark of the Boston Marathon bombings, a terror attack that led to the killing of MIT Police officer Sean Collier. April 22, 2013.

(04/22/13-Cambridge,MA) MIT Police Chief John DiFava is hugged by a member of the MIT community, shortly after a moment of silence that commemorated the one week mark of the Boston Marathon bombings, a terror attack that led to the killing of MIT Police officer Sean Collier. April 22, 2013.