A guard at a Marine Corps base in North Carolina was in custody Tuesday night after he shot and killed another guard in an isolated incident, officials said.

The guard fired an M4 rifle, killing another guard at the main gate of the base, Camp Lejeune, around 5:30 p.m., according to a statement from the base. The victim died of a single gunshot wound to the chest. The two Marines have not been identified pending notification of their families, the statement said.

The base was not placed on lockdown, as happened after a shooting at Fort Hood, Tex., last week, officials said.

“The base provost marshal has stated the incident is being considered neither as an act of terrorism nor an active shooter event at this time,” the statement said.