On Feb. 14, he told his parents what happened in a lengthy Internet chat: Members of his unit on patrol had killed "some innocent guy about my age just farming." He said he did not witness the killing.

But, he wrote, those involved told him about it and urged him to "get one of my own."

He said that virtually everyone in the platoon was aware of what was going on, but no one seemed to object.

"If you talk to anyone on my behalf, I have proof that they are planning another one in the form of an AK-47 they want to drop on a guy."