Senior Master Sgt. Kyle Zimmerman, the production superintendent assigned to the 28th Aircraft Maintenance Squadron, inspects a window during an active shooter exercise at Ellsworth Air Force Base, S.D., Feb. 22, 2018. Ellsworth AFB conducted an active shooter exercise, testing Airmen in nearly 20 locations on their ability to respond to different situations in their buildings. (U.S. Air Force photo by Senior Airman Randahl J. Jenson)