I'd add here that top instructor & sworn LE officer; Massad Ayoob also advises armed citizens to NOT yell any warnings or issue any commands when confronted with a violent felon in a home attack, just open fire and then deal with the subject(s) after you have them contained or help(local LE) get on scene.
I read Ayoob's older book; In The Gravest Extreme at my local public library 2 weeks ago.
He makes a valid point. Yelling or warning attackers may key them into your location or you could be distracted or even ambushed(some may say; bush-whacked,
). To use deadly force or fire at a subject, ONCE YOU CLEARLY ID THEM, is a sound practice.
I, for 1, would not yell; GET OUT or "I CALLED 911!", I'd ID the house-breaker, then use force if required in the critical incident.