Dion Harris, 28th Security Forces Squadron lead instructor, briefs Airmen from the 28th Mission Support Group on how to deal with an active shooter situation during a 28th MSG deployment readiness exercise in the Pride Hangar on Ellsworth Air Force Base, S.D., Feb. 14, 2013. During the session, Airmen were instructed to seek safe shelter and notify authorities if possible. (U.S. Air Force photo by Airman Ashley J. Thum/Released)