Article Photos: Slain MIT officer memorialized at campus service 1/12

This undated photo provided by the Middlesex District Attorney's Office shows Massachusetts Institute of Technology Police Officer Sean Collier, 26, of Somerville, Mass., who was shot to death Thursday, April 18, 2013 on the school campus in Cambridge, Mass. Thousands of MIT students, faculty and staff as well as law enforcement officials from across the nation are expected to attend a memorial service for fallen campus police officer Sean Collier. MIT officials say they are expecting as many as 10,000 people at the service at Briggs Field on Wednesday, April 24, 2013. (AP Photo/Middlesex District Attorney's Office)