507th Air Refueling Wing
Tech. Sgt. Darryl Lindgens, mock active shooter, attempts to gain entry to an office at the 507th Air Refueling Wing headquarters building during an active shooter exercise Aug. 11, 2015, at Tinker Air Force Base, Okla. This is the third active shooter exercise at the base this year. (U.S. Air Force photo by Tech. Sgt. Lauren Gleason)