The victim was inside their house and within their rights to be holding an unholstered weapon. The police did not (IIRC) identify themselves before shooting him.
If you hear a noise outside and it sound like a group of men rummaging around outside who might just decide to kick in your door, it does make sense to be inside waiting for them with a drawn gun.
Because this is what happens if you don’t. https://en.wikipedia.org/wiki/Cheshire,_Connecticut,_home_invasion_murders
I will again say, I don't know what goes on in this neighborhood, and it really makes a difference with respect to the home dweller's actions.
I think the best action for the armed citizen is to retreat, out of sight with weapon so as not to be seen. What advantage is it to be a visible target? Again, may well be within his rights, but also dead.
There was no one else mentioned so "within his rights" would not appear quite so ignorant. We should not be writing from the PC stylebook here. "Zer rights" would be as bad.