160204-N-SJ730-063 Naval Support Activity Bethesda Security personnel respond during an active shooter drill as part of the Navy-wide Solid Curtain-Citadel Shield exercise Feb. 4. Solid Curtain-Citadel Shield is an anti-terrorism force protection (ATFP) exercise designed to train Navy security forces to respond to threats to installations and units. (U.S. Navy photo by Mass Communication Specialist 2nd Class Hank Gettys/Released)