U.S. Air Force Staff Sgt. Rock Woods, 633rd Dental Squadron noncommissioned officer in charge of dental logistics, simulates being a casualty during an active shooter exercise at Langley Air Force Base, Va., Dec. 11, 2014. Airmen volunteered to act as victims during the exercise in an effort to provide the most realistic scenario. (U.S. Air Force photo by Senior Airman Kayla Newman/Released)