In some locales if someone is in your home while you are there, regardless if you entered after them, they're a danger to your life and it is permissible to use deadly force.

Home invasions and burglaries where someone is home are so rare where I live they make the state news when they happen.

The only time I've heard of someone being successfully sued was after executing a home invader who had already been shot and lying unconscious/dead, all caught on camera. Course they also went to jail.