"act like animals while in civilization"
okay
i guess we just not give a forget about it and move on?
"oh hey tim what happened over your summer"
"oh some dog came over and killed 13 of my cats brutally and ate them, some being kittens. nobody really cares though, just what an animal does, it received no punishment"
"oh cool"
Few things:
That's a lot of loving cats.
Why were they reachable by the neighbors dog? Did they enter his territory or did the dog enter the OP's yard?
Was the dog abused to the point that it was hungry enough to deviate from its normal dog food to eat raw flesh? Does it normally eat raw flesh without punishment?
Is this situation really any different than your cat or dog bringing home dead wild life, besides the ownership of the cats?
I'm not saying that the dog should have eaten the cats, I'm saying that you shouldn't leap the the conclusion that this "evil" dog ate the OP's cats for the hell of it and deserves to be killed without assessing what lead to him doing it.
Edit: Also, how did a single dog catch and kill 12 cats?