Your premise is wrong at the most basic level. The correct mode of action for a CCW holder is to hold in place, and if the shooter tries to enter the area he controls, take him out.
Private CCW holders can be compared to a minefield, what you are hoping for is the active shooter doesn't expect armed resistance and the CCW holder can get some shots in before the active shooter realizes he is being confronted.
If you hold in place and you hear someone coming down a blind hallway, do you shout out and ask if they are the police, the shooter or another good guy? If it's the shooter, you're shit out of luck, aren't you? If it's the police they may not believe you are a good guy. They may think you're the shooter trying to save his sorry ass.
And if you hold in place but can hear the shooter actively killing people in another part of the building, what do you do? Your gun becomes a joke to the people who are dying.
So you should check YOUR premise for
reality.
Just as an FYI, I'm a Democrat in favor for more gun control...however, even I can tell you aren't even being realistic here. It is pretty damn clear that you have no military or police training.
First of all, almost no gun owner is going to tell you that they own a gun in order to be a hero. They will almost always tell you that they own a firearm for some sort of personal or property protection. In an active shooter is running around 95% of people are going to find a way to get their happy ass out of that place before they get blasted to...that includes people that are carrying. If they are unable to escape, then sure...then they are going to try and hold up and barricade themselves in somewhere. And when you do that are you going to be yelling out and asking people who they are? **** no. You are going to stay the **** quiet and hope nobody finds you. IF police / SWAT are coming and they are properly trained they will be telling you who they are in a clear manner...because it doesn't matter if you are a shooter or a hostage they want you to know who is coming. Now if you are a dumbass and hear police tell you they are coming and you wanna sit there and try to shoot them anyways...sure you probably need to die anyways out of pure stupidity. On the other hand, 100% of rational people will lay down their weapon and let them know they are there and present themselves in a non-hostile manner.
If you are going to be for more gun control...as I am, at least have a good idea of what you are talking about before you say something.