"Sheba" was my brindle pitbull that I got as a puppy. I had her for over 15 years. She was my baby, the best dog I ever had. She used to cuddle on the couch with my cat and my toy poodle, and the children in my neighborhood loved to play with her. She was a 90 lb. face-licking lap dog. A part of me died the day I had to have her put down due to old age and arthritis, and a decade later I still miss her and get weepy when I think about her. Today I have several pit bulls on my route, and I love every one of them.
That being said....if a pit bull that I did not know charged at me or a loved one in an aggressive manner such as was seen in the video, I would blow it away without hesitation. I might be willing to allow a smaller dog or a mutt to bite me in order to avoid having to shoot it, but if we are talking pit bull or rottwieller or doberman then risk of serious injury or even death is simply too great.
The real tragedy here was the irresponsible owner of the dog who chose to drink in public to the point of gross intoxication and having seizures. By passing out drunk on the sidewalk, he put his dog in a situation where it felt it needed to protect him, which in turn put the police officer in a situation where he had no realistic alternative but to shoot the dog for his own safety.
My only concern with the officers actions was the fact that the muzzle of his gun appeared to be pointed at the man on the sidewalk, and a missed shot (or a round that passed thru the dog) could easily have riccocheted off of the street or curb and struck a bystander. Fortunately, there were no injuries other than those suffered by the dog.