We've been made aware of the fundamentalist Christian prostelytizing of the American military for many many years. My guess is this is more than an Afghanistani version of My Lai (http://en.wikipedia.org/wiki/My_Lai_Massacre).

What likely happened is this soldier was religiously indoctrinated and primed to be a "Crusader". When American soldiers were murdered as a reaction to the U.S. military burning those Korans, this guy snapped. He was outraged both as a soldier and as a Christian and felt he had to do something and felt he'd be justified in doing it. It was more Christian than military because he selected helpless mothers and children, not soldiers, and certainly not Taliban or "terrorists".

If it wasn't for the billions in rare metal deposits, I'm sure we would be out of that country by now.