Defense Secretary Chuck Hagel is ordering a review of physical security at all U.S. defense facilities worldwide, following the shooting Monday that left 13 people dead at the Washington Navy Yard.
Military and independent panels will undertake the same reviews that are to include security clearance policies. Hagel said Wednesday, "We will review everything. Where there are gaps, we will close them.''
The suspected gunman, private contract employee Aaron Alexis who was killed by police, got into the Navy Yard with valid identification. He had been undergoing mental health treatment at the Department of Veterans Affairs since August, but was not stripped of his security clearance.
The FBI says Alexis acted alone, but his motive is still unknown.
Alexis had previously been arrested in two separate shooting incidents in 2004 and 2010, and was cited several times for misconduct during his four-year naval service, which ended in 2011.
His Navy security clearance led to his hiring as an information technology specialist by a private defense contractor. The contractor said Alexis worked on at least six military installations in July and August without incident.
Monday's incident is the latest in a rash of deadly mass shootings in the United States. During an interview on the Spanish language television network Telemundo, U.S. President Barack Obama called for Congress to approve new gun control measures to keep guns out of the hands of the mentally ill.
Mr. Obama has ordered a review of security standards for government contractors and employees across federal agencies, and Defense Secretary Hagel has ordered a security review of all U.S. military facilities around the world.