You let your cat roam free while you were not around for an extended period of time, full well knowing that he leaves these chemicals out (and it is YOUR cat, not his responsibility). It sucks that your cat died and I feel for you on that but holy shit dude that's kind of excessive especially since it seems like you are in denial of the fact you had a large part in what happened. It was your responsibility to keep your cat safe and you failed. You can't change your environment but you are in control of your actions and you let your cat out despite knowing it wasn't safe. And then broke this guy mentally? Fucking psychotic behavior.