Posted by ChrisLCR: I think they already crossed that line when they broke into his house, don't you?
Why trap and barricade yourself in some bedroom if he could safely scare away or take out the threat if he had to from the stairs?
To significantly reduce the very real risk of being shot.
My Lord... at what point are we finally allowed to act to defend ourselves and our families in our own homes?
In most states, unlawful entry, perhaps made with force, will suffice, under most circumstances.
I'm no tactician, but being intimately familiar with the house, having the high ground on top of the stairs while half concealed seems to present a clear advantage to the home defender in the OP's situation.
Some say run to the bedroom and fire through the door at the first sign of forced entry. That may work in some situations, but the homebreakers can likewise shoot through the door first at you and your loved ones.
If there is a reasonably safe way of stopping the threat without having to trap yourself in a small room with possibly no way out, I believe it would be best to do so.