Three members of the U.S. Marine Corps were killed Thursday night in a shooting on the grounds of the Marine Corps Base Quantico, the Marines said. About 10:30 p.m., a male marine opened fire, killing two fellow marines before turning the gun on himself.

The identities of the shooter and the victim—one male and one female—are being withheld while the military notifies their next-of-kin. All three marines involved in the incident were assigned to work at the Marines Officer Candidate School on the base, Colonel David Maxwell, the base commander, said at a news conference early Friday.

“This is a tragic loss for our Marine Corps family,” Maxwell said.

Personnel were notified of the shooting by 11 p.m., Maxwell continued, with heightened security deployed throughout the 100-square-mile facility. The base resumed normal operations at 2:30 a.m.

A Pentagon spokesman said Defense Secretary Chuck Hagel “was saddened to learn of the shootings.”

“His heart and his prayers are with them and their families,” the spokesman, George Little, added. “He believes that the legendary strength of the United States Marine Corps will ensure that they are forever remembered.”

Quantico, with about 12,000 military and civilian personnel, is 33 miles south of D.C. In addition to being home to the Marines Officer Candidate School, it is alos the location of the FBI’s training academy.