WASHINGTON (Reuters) - Several gunshots were fired at a Marine Corps museum near Washington overnight, leading the FBI on Friday to search for someone who probably was once part of the Marine Corps and has a grievance against the military.

The FBI has linked three separate shootings at the Pentagon, a Marine Corps recruiting station in a Virginia suburb outside Washington and the National Museum of the Marine Corps, in Triangle, Virginia, 36 miles south of the city.

Investigators are working on the assumption that the second shooting at the museum that occurred late Thursday or early Friday is also connected, said John Perren, head of the FBI’s Washington Field Office, which is leading the probe.

“It may be that he feels that he’s been wronged by the Corps in his professional and/or personal life,” Perren told reporters. “We’d like to know what (that) grievance is ... and what we can do to try to help resolve it.”

He declined to comment on the weapon that was used and authorities were scouring a highway near the museum after the latest shooting for additional evidence that could help identify the shooter.

The timing of the shootings, which began on October 17, comes days before the annual Marine Corps marathon set for Sunday and officials said they will be tightening security for the race which attracts tens of thousands of runners and spectators.

No one has been injured in any of the shootings, which have all happened during the late night or early morning hours. Perren said it did not appear the individual was trying to hurt soldiers or civilians.

“We do not believe his intention is to harm innocent citizens or Marines. Acting out in this way, however, can eventually lead to disastrous and tragic consequences,” he said.

The shootings have revived memories of another rash of shootings eight years ago when a sniper shot and killed 10 people and terrified the Washington area over several weeks in 2002.

The Pentagon was a target of the September 11, 2001, attacks. In March, a gunman shot and wounded two security officers near a Pentagon entrance, and was killed in the process.