A 15-yr-old mutt who was an icon of a local neighborhood was shot four times in the head because an officer thought the dog was "suffering". The dog had a benign tumor on his neck.
Normally, if you think a dog is suffering, and you're not sure if the dog might have a guardian or family who cares about them, you take the dog to a vet, not plug him full of bullets.
Oh yeah, afterward, they threw the dog's body in the trash. Nice.