Those people sound like they were awful! I am so sad that one of your dogs died as a result of some human cruelty, but am glad that your other dogs will be ok.
Even though I don't like my neighbors attitude towards the handling of her dogs, and they (her dogs and the owners!) are a pain to have around, I'd still never poison them. Although I did tell her that if I caught them out chasing my horses for a third time then I'm going to catch them and call the pound. She'll be forced to pay fines for allowing them to run rampant and have to bail them out. Maybe then she'll take the steps on keeping him properly contained. I'm not mean, but just tired of having to catch and contain a dog that's not mine, one that chases my horses and cats, fights with my other dog, will be attacked my my Dane if she sees it in the yard, and steals/destroys supplements and treats from our shed and barn that cost quite a bit of money to purchase for the horses.