WASHINGTON, April 8 -- A U.S. Marine standing guard shot to death a fellow soldier on Tuesday at the main gate of the Camp Lejeune in the state of North Carolina, local media reported.

The suspect used a M4 rifle to kill the other guard in the shooting which occurred at around 5:30 p.m. (0830 GMT), base spokesman Nat Fahy was quoted as saying.

There were other sentries at the gate at the time of shooting, Fahy said, without disclosing further details.

The identities of the two guards were being withheld until their families were notified. The cause of the shooting remained unknown pending the investigation by the Naval Criminal Investigative Service.

This was the second shooting in the past week at U.S. military camps after the Aril 2 incident at the U.S. Army base of Fort Hood in Texas, in which a soldier committed suicide after shooting to death three fellow soldiers and wounding 16 others.