An active-duty marine reportedly shot and killed two fellow marines at Marine Corps Base Quantico in northern Virginia on Thursday night before turning the gun on himself.
"The shooter, an active-duty Marine, was pronounced dead of a self-inflicted gunshot wound by law enforcement at the scene," base commander Colonel David Maxwell said at a news conference, according to Reuters.
The names of the three active duty marines killed have yet to be released due to a pending family investigation.
Marine officials have reported that a relationship dispute is believed to have been behind the murder/homicide, which took place at the Officer Candidate School's barracks section at roughly 10:30 p.m., Thursday night.
The shooter was a male and the two victims were one male, one female.
A senior defense official called the incident "isolated," adding: "there was nothing random here," according to NBC News.
The Quantico Marine Base, which spans nearly 100 miles of northern Virginia, went into lockdown mode shortly after a 911 call was made about the shooting.
Local police officers and military police reportedly responded to the call within five minutes, according to NBC, and arrived to find one victim shot dead outside of the barracks, and the other victim, along with the gunman, shot dead inside the barracks.
According to Reuters, the base's lockdown was lifted around 2:30 a.m.
The three slain marines were reportedly all staffers at the base's Officer Candidate School, which trains enlisted personnel to gain commission as officers.
Thursday's shooting marks the second tragedy U.S. Marines Corps have seen in a week. On Monday, a mortal shell explosion at an army depot in Hawthorne, Nev., killed seven members of the 2nd Marine Expeditionary Force.
"This tragedy, as well as the tragedy in Nevada earlier this week, took the lives of Marines who volunteered to serve their nation," Pentagon press secretary George Little said, adding that Defense Secretary Chuck Hagel's "heart and his prayers are with them and their families."