Airman Keith Leflore, and John Bisbee, 28th Security Forces squadron defenders, clear a simulated hostile environment during an active shooter exercise at Ellsworth Air Force Base, S.D., Aug. 24, 2012. Active Shooter situations normally last no more than 15 minutes, but can result in major loss of life. Defenders must be able to quickly respond in order to prevent further loss of life. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)