U.S. Air Force Airmen from the 633rd Security Forces Squadron participate an active-shooter exercise at Langley Air Force Base, Va., Nov. 19, 2013. The 633rd SFS and the Hampton Police Department worked hand-in-hand during aspects of the exercise to ensure it prepared Langley personnel for an emergency situation. (U.S. Air Force photo by Airman 1st Class Victoria H. Taylor/Released)