Area military installations increased their security while police searched for additional shooters at the Washington Navy Yard.
The Navy, meanwhile, issued an "order to account" for all Naval personnel assigned to commands in the Washington metro area.
Commanders ordered personnel at the Washington Navy Yard, Joint Base Anacostia-Bolling and Fort McNair to shelter in place as military and District of Columbia police converged on the naval installation in Southwest D.C.
The commander of Fort Meade said visitors might experience delays as they attempt to enter the Army base in Anne Arundel County.
"As the events at the Navy Yard unfold, we will remain focused on the safety and security of everyone on Fort Meade," Col. Brian P. Foley said. "We ask that everyone remain vigilant and report any suspicious activity to local authorities."
A spokeswoman for the Walter Reed National Military Medical Center said the facility in Bethesda had also increased security, under orders of Naval District Washington. Spokeswoman Sandy Dean said she could not discuss specifics.
A spokeswoman for the Naval Academy also said she could not discuss security details.
"The Naval Academy is aware and monitoring the current situation at the Washington Navy Yard," spokeswoman Jenny Erickson said. "We are taking all of the appropriate measures to ensure the continued safety and security of our midshipmen, faculty, staff and our visitors."
Security was increased at the Pentagon in Arlington, Va., across the Potomac River from Washington.
The Navy said the order to account applies to active duty and select reserve personnel, family members and civilian employees. They were directed to muster through the Navy Family Accountability and Assessment System.
The Washington Navy Yard was the venue recently for the preliminary hearing of three Naval Academy football players who are accused of sexually assaulting a female midshipman last year when she was incapacitated.
Fort McNair is the home of the Military District of Washington.