Gunnery Sergeant Gus Covarrubias became the target of the preliminary inquiry after he described for the Las Vegas, Nevada, Review-Journal daily how he had hunted down and shot two Iraqi soldiers after a firefight.

"A preliminary inquiry has been initiated by the Naval Criminal Investigative Service to examine the circumstances surrounding the statements made by Gunnery Sergeant Covarrubias," the Marine Forces Reserve command said in a statement.

"The preliminary inquiry will determine if the actions described by Gunnery Sergeant Covarrubias during combat operations met the established rules of engagement and complied with the law of war."

A command spokeswoman refused further comment, referring media inquiries to naval investigators. A Naval Criminal Investigative Service spokesman could not be reached for comment.

In the interview published Friday, Covarrubias, 38, said he was searching for the source of a grenade attack during the April 8 battle and found an Iraqi soldier in a nearby home with a grenade launcher next to him.

Covarrubias told the daily he ordered the man to stop and to turn around. "I went behind him and shot him in the back of the head -- twice," he was quoted as saying.

Covarrubias said he noticed another Iraqi soldier trying to escape and also shot him, then grabbed their identification cards, a rifle and one of their berets for souvenirs.

Covarrubias, a 20-year veteran and former sniper, is assigned to the Second Battalion, 23rd Marines, a reserve unit from the western United States. He suffered a concussion in the firefight and has since returned home, the Review-Journal said.

In the interview, he was quoted as saying the killings were "justice." A military expert, however, suggested the first could have been a war crime.

John Pike, director of globalsecurity.org, said the investigation likely would center on whether Covarrubias shot the first Iraqi soldier after he had surrendered.

"The initial newspaper report made it sound as though he had captured the guy and he had executed a (prisoner of war), which is illegal," Pike said.

"In this case there seemed to be an element of premeditation."

Failure to accept surrender -- though a war crime -- is more common than generally thought in close infantry combat, he said.

"Surrendering's hard to do," he said. "It's dangerous because everybody's real charged up, everybody's real confused ... and it can be real hard to stop shooting."

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