What a sad, horrible end to your beautiful kitty, Bear, and how difficult for you and your daughter to witness it. It gives me nightmares to know your ex has access to your home. I hope you and your daughter are safe. Can't you bring charges against your neighbors? I know it wouldn't bring Bear back, but it might prevent the death or injury to other cats, small dogs, or even children.

RIP Bear. No animal deserves a violent ending like yours.
Play gently at the Bridge while you wait for those who truly loved you.