Tech. Sgt. Leegale Irving, 501st Combat Support Wing ground safety manager and simulated-active shooter, demonstrates the feelings of isolation an active shooter may exhibit prior to his simulated rampage at RAF Alconbury, United Kingdom, July 17, 2014. According to the Federal Bureau of Investigation, 20 percent of active shooter cases involve the shooter going mobile and moving to another location after the initial attack. (U.S. Air Force photo by Staff Sgt. Jarad A. Denton/Released)