First of all, it wasn't an atrocity (which in my mind implies premeditation).
Second, you ignore the part about the explosion just prior to the car arriving on the scene.
What would you think about a car coming down the road and ignoring orders to stop in this situation, just after an explosion, and a day after a car bomb went off?
Trigger happy, or prudent?
Very good assessment in my opinion. We don't know if the soldier screwed up...but the hidden bit of information we do know is that one soldier was hit by presumably 'friendly fire'. I understand the dynamics of combat and that FF is common (and in some ways not as common as you would expect in the chaos of a fire fight). But FF killed a soldier at a checkpoint? Did he walk out to the car and then they opened fire? Doesn't make sense - as described at least. The author appears to have bias, but none of us really know what happened. (It is also possible that our guys screwed up - consider the pressure they are under. Well, the pressure they are under if all the quagmire and drinking blood stories are actually true...lol.)
Gum