Airmen with the 90th Missile Security Forces Group make their way through an active shooter scenario during the Crow Creek Challenge on F.E. Warren Air Force Base, Wyo., Sept. 22, 2017. This is the 23rd year the Crow Creek Challenge has put the 90th Missile Wing’s defenders’ mental and physical capabilities to the test. (U.S. Air Force photo by Airman 1st Class Braydon Williams)