Military bases have standard THREATCON protocols they execute when there has been an active attack. As with other bases around the nation and the world, the Yard went to a lockdown mode, essential personnel only. In the big picture of things, USNA is a schoolhouse command, though a highly visible one, not an operational base with combatant ships and aircraft, or deployable units. Eventually it stepped back down to a lower THREATCON and resumed normal operations. Fairly quickly after that and in the year that followed, significant hardening was done to all military base gates and security procedures. Other incidents over the years have caused similar responses, such as the Marine Barracks bombing, the USS COLE attack, etc. Those types of events and responses are planned for.
COVID-19 has broken nearly all the usual patterns at USNA, a place used to fairly predictable schedules and rhythms, and has delivered a sustained tempo of unique stressors. No playbook for something like this!
USNA came together as a community to mourn grads who were killed.