The Marine guard at Camp Lejeune, N.C., who shot and killed another Marine on Tuesday appears to have fired the weapon accidentally, according to investigators.

The initial word from the Naval Criminal Investigative Service is that the Marine who fired an M4 rifle, striking and killing another Marine standing guard, didn’t intentionally fire the weapon, Nat Fahy, a spokesman for the Marines, said Wednesday afternoon.

However, investigators cautioned that it will take several weeks to confirm this.

The Marine who was killed, and who has not been identied yet, suffered a single gunshot wound to the chest at about 5:30 p.m. Tuesday and was pronounced dead at about 6:10 p.m. at Naval Hospital Camp Lejeune.

This shooting came less than a week after a military truck driver opened fire at Fort Hood, Tex., killing three people and injuring 16 others before taking his own life. That installation was locked down for several hours in the wake of the shooting.

Marines were quick to caution after Tuesday’s shooting that the situation at Camp Lejeune was not an active shooter situation.

The Marine who opened fire is still in custody and has not been identified yet, Fahy said.