MAYPORT, Fla. (Feb. 2, 2021) Naval Station Mayport Security Response Force Cpl. Keith Shaheen, left, a civilian patrolman, and Master-At-Arms 2nd Class Mark Doorenbos, center, play out security protocol with Hull Maintenance Technician 1st Class Lavelle Govia, assigned to the future Freedom-variant littoral combat ship PCU Nantucket (LCS 27), during an active shooter drill on base for Exercise Citadel Shield-Solid Curtain 2021. The exercise is a two-part, anti-terrorism force protection exercise that is being conducted nationwide on Navy installations, Feb. 1-12. The annual exercise is not in response to any specific threat, but is used to evaluate the readiness of fleet and installation security programs. (U.S. Navy photo by Mass Communication Specialist 2nd Class Alana Langdon)