U.S marine, 20, is found dead in apparent suicide while on duty at barracks in Washington DC
Lance Corporal Andrew J. Arista of Garden Grove, California, was found dead at approximately 2:45 a.m. at the Marine Barracks 8th and I's Annex location in D.C
Police are treating the incident as an 'apparent suicide,' according to a police report
When the Metropolitan Police Department arrived on scene, they witnessed CPR being administered to Arista
The marine succumbed to his injuries and was pronounced dead on scene at 3:07 a.m
While DC Police did not confirm how Arista died, a M4 colt carbine was seized at the scene as evidence, according to the report