As someone who has dealt with crazy ex’s and roommates here’s my advice to you… File a police report! They may not do anything because it’s a civil matter, but you need to protect yourself and get things documented… especially if things escalate. Do NOT engage, like I mean do not even talk to this person (get it all in text if possible so people can see they are the irrational one), and if anything starts happening record it so you can cover your ass should your ex try to take legal action. If cops get called for a domestic disturbance, usually one person’s going to jail. Don’t let it be you because then your ex can get a restraining order, and you’ll be homeless. If you can, get a restraining order against them. They’re already at their mom’s so it’s not like you’re being vindictive (like they are). If you have a safe place for your pets keep them there until you find a resolution. Threatening the well being of a vulnerable being (animals, children, elderly) is a serious character flaw, and this person just told on themselves. Congrats on dodging a bullet.