Why I can understand why a cop might become frightened at the sight of a large dog and shoot it proactively ("understand" , mind you, NOT automatically support or defend) there is no excuse for killing cats or kittens (or teeny little dogs, for that matter). There is just no defense that can be made for such mindless brutality.
Dogs can be effectively tasered. Shooting them is sick and evil, and should only be done under the most extreme circumstances. Each case should be reviewed as a police action shooting on the same level as if they had shot a person.