The 20-year veteran of the Marine Corps [Sgt. Covarrubias] said he found the soldier after dark inside a nearby home with the grenade launcher next to him. Covarrubias said he ordered the man to stop and turn around.

"I went behind him and shot him in the back of the head," Covarrubias said. "Twice." ... After killing the Iraqi soldier, he took the man's military ID as a souvenir.

...

"As soon as (the Iraqi soldier) had surrendered and obeyed a command to turn around, he was no longer an enemy combatant. He was a POW," said Pike, one of the nation's leading civilian experts on the U.S. military. "We do not allow our soldiers to execute POWs at their own discretion. And this, as described, looks like the summary execution of a POW."

...

"These kinds of incidents are a lot more common than anyone is ever going to let on. But it's usually not the sort of thing people talk about," Pike said. "The Iraqis quite possibly did it to us, and I'm not surprised we did it to them, but it's not supposed to happen."