(CNN)It was just before 3 a.m. on July 31, 2013, when a federal law enforcement officer left Room 634 of the Sheraton Syracuse University Hotel, stood underneath a flagpole, put a gun to his head and pulled the trigger. The single shell casing landed near a bench next to his body.
Shortly after police arrived to investigate the shooting, so did the taxi driver who was due to take the agent to his next assignment. The dead man lying on the ground was an armed federal air marshal, a plainclothes officer whose job was to protect aircraft from terrorists. He took his life just hours before his next scheduled mission, a US Airways flight from Syracuse, New York, to Washington.