Not gonna use slugs or even 00 buckshot inside. At close range, #4 buckshot is going to be plenty devastating.
The pattern of standard 8shot is about 13-16 inches at 25 feet. This means a far tighter pattern at room length, say 15 feet. So, go big on the first couple shells (e.g., = or > than 6 shot) to catch the scumbag on the first/second shot, slow down, or disable, followed by buck, if needed. And ignore the possible legal issues with how you rack the shells.
And less accurate too. If someone you're trying to shoot is standing next to someone you're trying to protect, you don't want to fire shot. Slugs aren't as accurate and if you over-penetrate with slugs, you've got a real problem on your hands.