Active Shooter Exercise
During an active shooter exercise, members of the Air National Guard, the Phoenix Police Department, the Federal Aviation Administration and the Transportation Security Agency work together to execute proper breaching and clearing techniques, at the 161st Air Refueling Guard base, Phoenix, June 4, 2011. This exercise helps to improve interagency communication and coordinate strategic planes. (U.S. Air Force photo by Staff Sgt. Courtney Enos/Released)