Quantico Marine base on lockdown following shooting By Jake Carpenter and Alison Harding, CNN March 22, 2013 -- Updated 0600 GMT (1400 HKT) The shooter is held up inside a building He is believed to be a Marine, but the motive is unknown (CNN) -- A Virginia Marine base was on lockdown early Friday morning following an isolated shooting incident, authorities said. The shooter is holed up inside a building at the Quantico Marine Base, said 1st Lt. Agustin Solivan, a Marine Corps spokesman. There appears to be one casualty in the shooting late Thursday night, but the condition of the victim is unclear. Both the shooter and victim are still at the scene, he said. The lockdown was announced across the base using a public address system. Everyone was ordered to stay in their homes with the door locked. The shooter is believed to be a Marine, but the motive is unknown, according to Solivan.