Perhaps the dog did something terrible, attacking a child for instance, that might give a man ( a very pitiful man ) the motive to take the dogs life. I just can't fathom how anyone could do such a thing without motive, not that it excuses him/her for doing it. Don't get me wrong though, i love dogs and have 3 black labradors and one of them had 10 puppies, a joyful occasion i must say.