The Massachusetts Institute of Technology will hold a memorial service later this week to honor a slain campus police officer. Sean Collier, who had been an MIT officer since January 2012, was shot to death while sitting in his MIT police cruiser on campus. One or both of the two men who are suspected in the Boston Marathon bombings allegedly shot Collier, authorities say. One of those men is now dead; the other is in custody. Tamerlan Tsarnaev was killed in a gunfight with police, and his brother, Dzhokhar, has been hospitalized after authorities apprehended him.