At first when I saw this I was thinking it was completely out of order to shoot the dog, especially right in front of the owner, god knows what I would do if anyone killed my dog right in front of me...
But then again, when a dog is trying to bite me, and once dogs attack you viciously they don't just bite, they hold on and try to drag you around and basically tear your limb off you, as well as the fact it's a Rottweiler, I probably would have done the same thing out of instinct.