Evil people are everywhere. Neighbors have done this to other neighbors pets, done to husbands, wives, biz associates, on and on.
Ya gotta be careful of who ya might piss off.
One of the reasons I get to know my neighbors and make sure my dogs know them. It also gives me a chance to see how the neighbors interact with the dog.
Had a psycho neighbor who poisoned my blue merle collie when I was away at college. Rat poison. Come to think of it, the other neighbor across the street stalked me by calling me on the phone when I was home for weekends. Maybe it was him. He stopped calling when I witnessed to him.
It take a certain kind of evil to give a dog something they KNOW will kill them..and for what, some stupid dog contest..I have heard how crazy these things can get..these dog owners can spend between 50-100,000 to get their dogs ready for the contest