Active Shooter Exercise Naval Support Activity Mid-South security forces and Shelby County Sheriff's officers help simulated injured personnel during an active shooter exercise in Millington, Tenn., Feb. 6, 2019. SHARE IMAGE: Download Image: Full Size (0.46 MB) Photo By: Navy Petty Officer 2nd Class Mason Gillan VIRIN: 190206-N-MU551-0305.JPG Photo Gallery