NBC reports that a US Marine killed two staff members and then died of a self-inflicted gunshot wound.
Officials state that the shooting was an isolated incident and "there was nothing random here."
The staff members who were killed were a man and a woman. Their names, and the name of the gunman have not been released yet.
Col. David W. Maxwell told reporters at a press conference on Friday that authorities are certain that no one else died in the shooting and the lockdown at Quantico was lifted early Friday morning.
The shooting happened at some point on Thursday night, with authorities called to the Marine Corps Base in Quantico at approximately 10:30 p.m.
The situation was first described as a standoff, but Col. Maxwell stated on Friday morning that there was no standoff.
NBC reports that Marine base spokesman Lt. Agustin Solivan later clarified some of the details of the shooting, stating that authorities had the shooter "isolated" in a barracks dorm room at the base's Officer Candidates School.
This is the second Marine Corps tragedy this week. On Monday, a mortar shell exploded in its firing tube during an exercise at Hawthorne Army Depot in Nevada. Seven Marines in the 2nd Marine Expeditionary Force were killed and eight others were injured.