Airmen from the 99th Civil Engineer Squadron Fire Protection Flight carry stretchers to out to simulated casualties of an active shooter scenario during a base exercise at Nellis Air Force Base, Nev., May 12, 2016. In addition to the active shooters, the track had a simulated bomb detonation and another simulated bomb that was planted. (U.S. Air Force photo by Airman 1st Class Kevin Tanenbaum)