A 51st Security Forces Squadron military working dog scours a building with its trainer during an active shooter exercise at Osan Air Base, Republic of Korea, May 6, 2016. Osan’s defenders neutralized the simulated active shooter minutes after they entered the building. The scenario officially kicked off the week-long readiness exercise, Beverly Herd 16-01. (U.S. Air Force photo by Tech. Sgt. Travis Edwards/Released)