That was stupid1. The dog is not attacking. He's being friendly and bouncy, just like he was on the street. Any reasonable adult who is competent to be in a position of public trust should know that.
2. Why was the cop even there?? From watching the full video, I think he just had a bug up his ass that the dog ran up to his car. Didn't require a home visit. Literally one sentence out the window to the kids about not letting their dog go into traffic.
3. He's using excessive force for the situation. Discharging a gun in a residential area with children around is not zero risk to humans. Killing the dog instead of accurately assessing his body language, or getting back into the car, was unnecessary. He didn't even tase him, just went right to lethal force.
This cop is a shit and if the world were other than a totally unfair place, he'd no longer be breathing, and he would have been--sloooowly and without mercy--relieved of his cock and balls first.