Maj. Gen. Richard F. Natonski, commanding general of the I Marine Expeditionary Force, said that a review of the evidence showed the Marine's actions in the shooting were "consistent with the established rules of engagement and the law of armed conflict."
The corporal was not identified in a two-page statement issued by Camp Pendleton, the headquarters of the expeditionary force north of San Diego.
The Nov. 13 incident was videotaped by Kevin Sites, a freelance journalist on assignment for NBC.
The shooting occurred when a Marine unit entered the mosque and found five men wounded in fighting at the site the day before, when another Marine unit clashed with gunmen apparently using the mosque to fire from, according to Sites' broadcast.
In the video, as the cameraman moved into the mosque, a Marine in the background can be heard shouting obscenities and yelling that one of the men was only pretending to be dead. The Marine then raises his rifle toward an Iraqi lying on the floor of the mosque and shoots the man.
Before the opening of the Nov. 8 assault on rebel-held Fallujah, Marine commanders told infantrymen that the rules of engagement allowed for use of deadly force against men of military age deemed holding hostile intent, even if the enemy didn't fire on the Marines first.