Always be sure of your target and what lies beyond it.
I would say always but someone could probably think of a scenario where he wasn't, but I can't.
I agree, but it was a moving target. The guy apparently just walked up. Perhaps Cheney checked before the Covey was flushed out and the area was clear. If a person suddenly runs out in front of a car at the last second, it's hardly the driver's fault if they get run over. Same scenario here.