A Marine shot dead two fellow service members at a base in Quantico, Virginia, then killed himself, the Marines said on Friday.
The shootings took place late on Thursday near the officer candidate school at the Marine Corps base in Quantico, and all three people who died were active-duty Marines, base commander Colonel David Maxwell said.
"The shooter, an active-duty Marine, was pronounced dead of a self-inflicted gunshot wound by law enforcement at the scene," he told a news conference carried by local media.
Maxwell gave no motive for the shooting and an investigation is under way. The two slain Marines, a man and a woman, were permanent personnel assigned to the officers school, as was the shooter, he said.
The base, known as "the Crossroads of the Marine Corps," was locked down shortly after a 911 call about the shooting at 10:30 p.m. The lockdown was lifted at about 2:30 a.m. on Friday.
Maxwell said all the shootings took place at the base's Taylor Hall. The incident was initially reported as a standoff with the suspect barricaded, but Maxwell said it was neither.
Identity of those killed was withheld pending notification of relatives.
The incident came after seven Marines were killed on Monday by a mortar explosion at an Army munitions depot in Nevada during a live-fire training exercise.
In that incident, a 60mm mortar round exploded prematurely in its firing tube. Eight other service members were wounded.
It prompted the Marines to suspend use of 60mm mortars pending a review.
Secretary of Defense Chuck Hagel was saddened by the Quantico shootings, the Pentagon said in a statement.
"This tragedy, as well as the tragedy in Nevada earlier this week, took the lives of Marines who volunteered to serve their nation. His heart and his prayers are with them and their families," the statement said.
Quantico, about 40 miles south of Washington, is also home to the FBI's training academy.