U.S. Air Force Staff Sgt. Nicole Johnston, 633rd Security Forces Squadron, NCO in charge of Police Services and Confinement, hides from incoming SFS members as the active shooter during an exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. Shortly after Johnston fired shots, 633rd SFS first responders infiltrated the building eliminating her as an active shooter. (U.S. Air Force photo by Senior Airman Kimberly Nagle)