Published: Oct 29, 2010 4:14 PM EDT
Updated: Oct 29, 2010 1:14 PM EDT

WASHINGTON (AP) - Authorities say a gunman who fired shots at a Washington-area Marine Corps museum and may have been responsible for three similar incidents may have a grievance against the U.S. Marine Corps.

FBI Assistant Director John Perren says investigators believe the person takes issue with the institution of the Marines, but not those serving in uniform. Perren says the person has gone to lengths to make sure no one has been hurt.

Someone fired shots at the museum in Triangle, Va., between 9 p.m. Thursday and 6 a.m. Friday. It is the second time in less than two weeks someone has shot at the museum. Someone also recently shot at the Pentagon and a military recruiting center.

The FBI has said the first three shootings are connected, and investigators say they assume the fourth is connected as well.