An individual, posing as a casualty, lays in front of the 633rd Civil Engineer Squadron customer service desk during an active shooter exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. During the exercise, four individuals were confirmed deceased and six injured after a disgruntled customer attacked personnel in the building. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

U.S. Air Force Staff Sgt. Nicole Johnston, 633rd Security Forces Squadron NCO in charge of police services and confinement, took on the role of active shooter during an exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. Johnston took action as the shooter after showing signs of irritation with customer service employees. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

U.S. Air Force Staff Sgt. Nicole Johnston, 633rd Security Forces Squadron, NCO in charge of Police Services and Confinement, hides from incoming SFS members as the active shooter during an exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. Shortly after Johnston fired shots, 633rd SFS first responders infiltrated the building eliminating her as an active shooter. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

U.S. Air Force Airman 1st Class Brett Nott, 633rd Security Forces Squadron installation entry controller, calls the control desk to inform them he apprehended the active shooter during an exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. Nott, eliminated the threat of the active shooter after a simulated shoot out. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

U.S. Air Force Staff Sgt. Jarrett Sanders, 633rd Security Forces Squadron Base Defense Operations Center controller, and his team clear the 633rd Civil Engineer Squadron building during an active shooter exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. After the active shooter was apprehended, more members of the 633rd SFS, patrolled the building to ensure there were no other threats. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

Members of the 633rd Security Forces Squadron clear rooms during an active shooter exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. The 633rd SFS members checked each door and office to ensure there were no further threats. (U.S. Air Force photo by Senior Airman Kimberly Nagle)

A simulated gunshot victim lays on the floor at the 633rd Civil Engineer Squadron building during an active shooter exercise at Joint Base Langley-Eustis, Va., Dec. 15, 2016. After the building was cleared by the 633rd Security Forces Squadron, first responders from other agencies arrived to treat the individuals with simulated injuries. (U.S. Air Force photo by Senior Airman Kimberly Nagle)