The FBI said, Friday, a gunman who recently fired shots at the Marine Corps Museum may be holding a grudge against the U.S. Marine Corps.

Shots were fired at the Washington, D.C.-area museum between 9 p.m. Thursday and 6 a.m. Friday. This was the second time in two weeks that someone had shot at the building.

A gunman also recently fired shots at the Pentagon and a military recruiting center. No one was injured in the shootings. The FBI believe the same shooter is responsible for the separate incidents.

John Perren, the acting assistant director for the FBI's Washington field office, said investigators believe the person has an issue with the institution of the Marines, but not those serving in uniform.

Perren said the person has gone to lengths to make sure no one was hurt in the shootings, and authorities don't believe the gunman wants to harm citizens or Marines.