OK, I see where you going now, and I somewhat misunderstood your comment.
I would say go with your own judgement as the situation develops, I may be yelling "stop", or "drop the weapon", but I'm going to shoot until either they comply, fall down dead, or I run out of bullets, which ever comes first.
You need to call 911 as absolutely soon as the situation permits so calling an ambulance doesn't matter, they will dispatch one along with the cops.
2 things to keep in mind, you may drop a deer with one shot from your favorite rifle, chances are that will not be the case with a handgun round, it's very important to keep putting rounds into the BG until he stops doing what made you shoot him the first time.
Second, you are responsible for every round you fire, with pavement, rocks, and all the other things that can cause a ricochet, and the long distances that bullets are able to travel, warning shots are the worst ida in the book, after "shooting to wound". The safest place for your bullets is in the BG, barring over penetration you are far less likely to get sued by some innocent schmuck.
As for what Ellis posted, there was a story going around about a woman being asked why she shot her attacker 6 times and she replies " Because the other times I pulled the trigger it just went click".