A U.S. Marine died of a gunshot wound to the head from another Marine's M16 rifle, military officials said Saturday. He was the 46th serviceman to die in Operation Desert Shield.

The victim was identified by Marine headquarters in Washington as Lance Cpl. James B. Cunningham, 22, of Glendale, Ariz. He was asleep in a tent camp at the time of the shooting Friday, officials said. They said the rifle discharged a single shot.The incident is under investigation, and two Marines who were in the tent at the time are being questioned, officials said. No other details were available.

So far, 43 other servicemen have died accidental deaths, one apparently died of natural causes and one committed suicide, according to military records.