I don't have anything special to add. It sucks, but try to remember the good times. I lost 2 cats pretty close to each other. The first one (porkchop) went bad real quick. I had to feed her churu through the weekend because she couldn't eat anything else. We had her euthanized at home and her sister was able to have more closure.
The pain will always be there but it will lessen. The 2nd one was cream cheese (in my profile pic) he died at 6 months to some rare brain disease. That one still hurts because he was so happy and excited about life. It still feels raw if I dwell too much. The first time I got thing from my phone about "check out these photos that you made a year ago" and it was his face and jumping around was hard. Just be aware how technology might surprise you with shit like that. I feel for you.
For anyone like me that didn't know what other people were talking about.
But yeah, fuck that dude. That's some projection claiming that you groomed him. wtf.