The Defenders of the 28th Security Forces Airmen use M-9 and M-4 weapons loaded with simulated munitions during an active shooter exercise at Ellsworth Air Force Base, S.D., Aug. 24, 2012. The rounds provide a more realistic experience for Defenders, allowing them to employ the same tools, tactics, and procedures that can enhance their survivability during real-world situations. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)