Pokemon Porn Story: What to do when your dog is victim of an unprovoked attack?

My dog was attacked by a pitbull mix last nite, who tied to a pole outside his hse on a 20 ft rope, unsupervised. My dog is a chihuahua and is very lucky tto be alive . He is going to be all right! We were on our way home from the park–my dog was on a short leash. the owners paid the vet bill and said the dog had never done anything like that before. They said he plays with the chihuahua across the street all the time. I hope they dont leave him out like that any more. They said they just moved there. I plan on walking by (without my dog) to see if the situation has changed. they seem genuinely sorry, but I hope it doesnt happen to some other unsuspecting dog. Why would this happen? Maybe new environment, or maybe being tied like that makes the dog feel vunerable? They also said their dog likes chase cats but has never hurt one—maybe he smelled my cat on my dog? They dont seem like the type of people who would try to make a dog aggressive. They have a catahoula hound dog too and they have had not any problems between them. I would like any comments and discussion about this as this has upset me very badly!