I have to say that I wished the cop could have used less deadly force, taser, rubber bullet, mace or something like that on the dog. They are too quick to shoot animals and people. In this case, the reaction of the cop was expected although I don't encourage killing any animal or person unless absolutely necessary, with this dog, I personally don't think it was necessary.
I was going to a very large, open area off leash dog park for over thirty years with my dogs. I had met many, many Pitbulls who were very well socialized and cared for by their owners. Those dogs were very friendly with me, my dogs and other dogs in the park. They were also gentle with people and children there. They can also be gentle with cats and other small animals if they have exposure at a young age and are trained properly. Most dogs who behave badly, do so because their owners trained them to attack, abused them or did no socialization training whatsoever.
They just mentioned the woman John was talking about on the news while we were eating, I told my husband that was the same location as the cop who shot the young dog. These cops need some training themselves, IMO.