The shootings, which numbered five in all, occurred between mid-October and early November of 2010. Two occurred at the Marine Corps museum, one targeted the Pentagon, and two separate incidents happened at the Coast Guard and Marine recruiting stations in Chantilly and Woodbridge, Va.
In each case, police say someone fired shots at the buildings in the early morning hours, or late at night. No one was injured, and several months later, no suspects have been arrested.
Lindsay Godwin, spokesperson for the for the FBI's Joint Terrorism Task Force, says investigators need assistance to change that.
"We're still reaching out to the public for any information that they might have, or any behaviors that they might have observed last fall that could lead to some new information coming in," she says.
The bureau is offering a reward of up to $20,000 for information leading the arrest and conviction of the person, or persons responsible for the shootings.