Is it a red flag my boyfriend says he’d kill my dog for killing his cat?

My dog (male) bit my boyfriend, and my boyfriend said that he would have to kill my dog if he ever killed his cat. He said he couldn’t even describe the anger he would feel. That nothing could stop him from killing him. He said that if my dog kills his cat, that there would be two broken hearts. How much of a red flag is this lol I would never kill an animal, but I know how mad I would be if another animal would kill my cat or dog. Would this eventually lead to him turning on me?

Is it a red flag my boyfriend says he’d kill my dog for killing his cat?
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