First Sgt. Kim Chinn, a Prince William County police spokeswoman, says multiple shots were fired sometime after the museum closed Thursday night. The museum is in Triangle, Va., about 30 miles south of the Pentagon.
Bullet holes were first found at the museum Oct. 17. Two days later, shots were fired into two windows at the Defense Department in suburban Virginia.
A third military office - a Marine Corps recruiting station in Chantilly, Va., outside Washington - was shot at late Monday or early Tuesday.
Ballistics testingreports CBS News Correspondent Bob Orr.
No one was hurt in any of the shootings.