U.S. Air Force emergency responders carry a simulated casualty using a litter, at Kadena Air Base, Japan, during an active shooter exercise May 4, 2016. During the scenario, a lone simulated gunman invaded the 18th Wing Legal Office and fought against 18th Security Forces Squadron emergency responders. The exercise provided a sense of realism and better prepared the responders for future real-world contingencies. (U.S. Air Force photo by Staff Sgt. Maeson L. Elleman/Released)