He didn't hit him. Either he was a lousy shot, or he didn't intend to hit him.
I see nothing wrong with firing a shot over the head of someone who was running away from your property as if they had done something. Wife may have overreacted, but the Husband seems to have behaved reasonably in my opinion. Now if he had hit the kid, that would be a different animal.
Youre that confident that you wont hit anything down range when firing over someones head? There is no circumstance in which one should fire a warning shot. Period.