U.S. Air Force Chief Master Sgt. Thomas Trottier, 4th Medical Group superintendent, plays the role of a disgruntled airman during an active shooter exercise at Seymour Johnson Air Force Base, N.C., Aug. 24, 2013. The 4th Fighter Wing routinely conducts readiness exercises to test and enhance airmen's skills and proficiency. (U.S. Air Force photo by Airman 1st Class Brittain Crolley/Released)