Is it okay to get my 7 year old son a pet cat?

We got him some rabbits two years ago and he tortured and killed them. I came home one day and found blood all over the kitchen table. I went up to his room and found the rabbit heads on top of sticks. Do you think enough time has passed for him to get another pet? He's requesting a cat. We think it might help with his behavioral issues. He's got a lot of anger issues and throws tantrums and threatens me a lot and he punched me last week, we think it might get nickled in the buck if he has an animal companion to take care of to help him learn to be more polite and caring.