U.S. Air Force Staff Sgt. Kelly Eaton, 633rd Security Forces Squadron military working dog trainer, prepares to move an injured individual during an active shooter exercise at Langley Air Force Base, Va., Dec. 8, 2011. The exercise tested the ability of emergency responders to respond to chemical, biological, radiological and nuclear situations, and engage in an active shooter and/or hostage situation. (U.S. Air Force photo by Airman 1st Class Kayla Newman/Released)