Wow. That is horrifying. Anyone who would harm or even kill non-human animals is likely to "graduate" to humans. I would call the police immediately and have them investigate. If he is caught with antifree and the cat has antifreeze in its system (would require a necropsy) and at least three of her cats has died the same way, he might be able to be convicted at least on circumstantial evidence.
Animal law is my primary area of interest and expertise. Please tell me more so that I or someone else can help you.
Thank you!
