Virginia Tech police Officer Deriek Crouse was shot and killed on Thursday, Dec. 8, 2011, during a routine traffic stop on the school's Blacksburg, Va., campus. (AP Photo/Virginia Tech)

Virginia Tech police Officer Deriek Crouse was shot and killed on Thursday, Dec. 8, 2011, during a routine traffic stop on the school's Blacksburg, Va., campus. (AP Photo/Virginia Tech)