Gunman on the Loose in D.C. May Have Vendetta Against Marine Corps

The FBI says an unidentified gunman who fired shots at the Washington-area Marine Corps museum and is believed to be responsible for three similar shootings may have a vendetta against the U.S. Marine Corps.

John Perren, the acting assistant director for the FBI's Washington field office, said during a press conference that investigators believe the person takes issue with the institution of the Marines, but not those serving in uniform. The shooter has made sure not to hurt anyone in the attacks and authorities don't believe the person wants to harm citizens or Marines.

The latest shots were fired overnight at the National Museum of the Marine Corps in Triangle, Va. -- the second time the facility has been targeted in a month.

The shooting occurred just hours after the FBI linked a shooting that took place overnight Monday at a Marine recruiting center in Chantilly, Va., with a previous shooting at the Marine Corps museum and another at the Pentagon.

FBI Assistant Director John Perren said the overnight shooting bears the hallmarks of the others, but said authorities need to conduct forensic tests to see if they are connected.

Museum staff came into work Friday morning and found new bullet holes, a public information officer at the museum told Fox News.

No artifacts were damaged and no one was hurt, the officer said

FBI confirmed Thursday that ballistic evidence showed the same weapon was used in the previous shootings.

The latest of those shootings occurred at a vacant Marine recruiting station in Chantilly, Virginia sometime between Monday night and Tuesday morning.

In the early morning hours of October 19 police and FBI investigators responded in force when six shots were fired into the south side of the Pentagon, leaving bullets embedded in two different windows. At the time police said the weapon used was believed to be a high-powered rifle.

And just two days earlier police in Quantico, Virginia responded to a similar attack on the Marine Corps Museum, where bullets were also fired at windows in the early morning hours.

The most recent shooting also comes just days before the Marine Corps Marathon, which  is set to take place in Washington on Sunday morning.

Authorities have yet to identify any suspects in the shootings, but are working under the assumption that the individual was part of the Marine Corps. and possibly dealing with a  traumatic event such as loss of a job, financial problems or divorce.

"We'd like to know what this grievance is and what we can do to try to help solve it," Perren said.

Perren urged anyone who may have information about the suspect to contact authorities and told people to quickly report gunfire or suspicious activity.

Pentagon spokesman Col. Dave Lapan said Friday that security would be even tighter than usual for the Marine Corps Marathon because of the recent shootings. The Pentagon is a staging ground for Sunday's race.

Prince William County Police Department, the Quantico Marine Corps base military police and the FBI were investigating to see if the same weapon was used in the most recent shooting.

Fox News' Justin Fishel, Mike Levine, James Sprankle and the Associated Press contributed to this report.