Counting shots is a bit disingenuous, as "one in the chest, one in the head" double-tap might as well be a single shot for the sake of argument. Me personally, I might think about not shooting people in the chest when they might be wearing a bomb-vest, but maybe I'm just overly cautious.
I think the problem more than anything else is that the shooting of an unarmed man is going to be seen as an execution by many parties regardless of how much anyone dissects the actual fire-fight. And being seen to follow the rule of law is nearly as important as just following it.
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"There is a time when the operation of the machine becomes so odious, makes you so sick at heart,
that you can't take part" [Mario Savo, 1964]