Cats should be kept indoors, but moreover your neighbor is a piece of shit and I hope he gets what he deserves. Get a super soaker you fucking monster, shooting someone's pet with something that travels around 200 mph is a bad look. After he baited them at that, I understand that wasn't his intention but the cats are just living by their basic instincts, it's not their fault. If he really was interested in stopping them rather than being cruel humane traps are cheap, just do what normal fucking people do, catch it, drive it 5-10mi, and release it somewhere it's no longer your problem, or drive it to the nearest no kill shelter. But no, can't be a decent human, it's more fun to break their ribs and possibly let them slowly internally bleed to death because they committed the crime of wanting to eat.

I'd rat him out for animal cruelty right now if I knew his name and location.