Prince William County police blocked the entrance to the National Museum of the Marine Corps Friday, after shots were fired at the building overnight -- the second such incident at the museum in a month.
In Virginia, the National Museum of the Marine Corps remains closed Friday as FBI and local police continue their investigation into who fired shots at the building overnight.
This is the second time shots have been fired at the building this month.
All day, police have been turning away would-be visitors to the museum at its entrance off of Jefferson Davis Highway in Triangle, Va.
Quite a few of those potential visitors are out-of-towners, arriving to the D.C. area early for Sunday's Marine Corps Marathon.
Most say they're not worried about safety at the marathon--but will welcome the heightened security due to the string of shootings targeting military facilities in the D.C. area, including the Pentagon, a staging area for Sunday's race.
At a press conference held at FBI headquarters, investigators said they're working behind the assumption that the shooter is a former marine who has a grievance against military institutions, but does not wish to harm citizens or service people.