This is simply awful, if true — and it appears it is:

A U.S. soldier was taken into custody in southern Afghanistan on Sunday, a few hours after he opened fire on Afghan civilians, killing 15, U.S. and Afghan officials said.

The shooting took place at approximately 3 a.m. as a lone soldier left a checkpoint in Kandahar province’s Panjwai district and opened fire on civilians in two villages, said Javed Faisal, the director of the provincial government’s media center.

Citing preliminary reports, Faisal said at least 15 people were killed and five were wounded. Provincial authorities said they were awaiting news from an investigative team sent to the villages before releasing a definitive death toll.

The BBC reports that the death toll is 16.  The US has not formally acknowledged that the shootings were perpetrated by an American soldier, but are investigating the incident:

Lt Gen Adrian Bradshaw, deputy commander of Nato-led forces, said he was unable to “explain the motivation behind such callous acts”, adding that “our thoughts and prayers are with those caught in this tragedy”.

The soldier has not been named, but is thought to be a staff sergeant.

He is reported to have walked off his base at around 03:00 local time (22:30 GMT Saturday) and headed to nearby villages, moving methodically from house to house.

If this is true, this will make the Koran burnings look like an Occupy protest.  Atrocities happen in every war even if they aren’t policy, but they can inflame the populace and make it impossible to constrain them.  That may happen even if the shooter turns out to be someone else, a possibility that looks fairly unlikely at the moment anyway:

Maj. Jason Waggnor, a U.S. military spokesman, said several civilians wounded in the shooting were being treated at American medical facilities. He said there is no information yet on the shooter’s motive.

“He walked right off base, started shooting civilians, and returned to the base and turned himself in,” Waggnor said.

Expect some more high-level apologies if this turns out to be accurate, and this time I doubt anyone can argue with the need to offer them.