Well Stated.

A PROACTIVE DEFENSE by OFFENSIVE MEANS

The Best defense is ALWAYS a Strong Offense

As a pilot in FL, I would just take off the right door, load the body and do a steep turn over the swamp. Let the poor alligators get indigestion.

I should note after re-reading. If the shooter was right behind me, I'd engage them immediately. You are very likely the first target, and no value in waiting on the floor:
- control the firearm direction,
- attempt to render the firearm harmless (take away, discharge rounds in safe-ish direction,
- disable it (drop magazine)),
- subdue the shooter (strike throat, head butt face, take to floor, break arm - action depends on relative positions).
Hopefully the ARMED CITIZEN comes over to help, and puts them down in the middle of this mess.

The weapons held by the shooter were not mentioned.

WHY would you expect an ARMED CITIZEN to carry a long gun while shopping?

It doesn't even have to be a "lethal" object

Just anything that will keep him ducking while others close by can take him down, take his weapons and KILL THE BASTARD
NO TRIAL, no funeral, no cremation

Flight at least miles offshore and dropped off fore shark food.

No name released, not even race....

Just the political positions held to show that, ONE MORE TIME, it was a LIBERAL with a gun

First I smack the snot out of the person with the cellphone because in this day and age their dumb a$$ is probably going to try and video the situation, then I look for something lethal to wield and I take the armed persons back to try and find or help neutralize the threat.

Less likely to be using a pistol, if they are another shooter.

Like Will Smith, "Those books are WAY too advanced for that little girl,..."

I assume this is a hypothetical question highlighting the foolishness of waiting for the police.
- Yes, waiting is foolish.
- Hit the floor, and hope the armed guy (unfortunately not you) shoots the cowardly nutter dead, so the taxpayers only cover an autopsy, there is only one story, and not a prolonged irrelevant sobbing review of his sordid past.

Dead is great. Before the shooting best, during ok, after? take what you can get.

Three words: shoot the bastard.

IF you aren't armed, dropping out of the line of fitre of someone behind you is always a good idea.

I wrote his script.

He can either follow the script or he will be replaced in the rewrite.

It is not clear what we have the disagreement on.

It is clearly spelled out that the Armed Citizen intends to STOP the shooter.

Had the sentence been that "the Armed Citizen already drawing a handgun" without specifying his intention, you'd have a point.

That was not the case.

You made up the scenario. How did you know the citizen was friendly and able to handle a firearm?

"you notice an Armed Citizen Already drawing a handgun to stop the potential shooter.."
It makes an assumption that the citizen is drawing to stop the shooter. Making that assumption could be fatal.

Because he is aiming at the shooter.

That is straightforward enough.

IF your threat Assessment" and "Situational Awareness" skills are that lacking DO NOT ARM YOURSELF
You don't posses the intellect necessary

Especially if unarmed.
Not a bad idea if armed even in a so-called "gun free zone." Something me dino violates all the time if there is not a metal detector.

Me dino would be pulling my own concealed carry and backing away from that "armed citizen." Hopefully, I'd be close to something I could hide behind.
On the other hand, if I clearly can tell the "armed citizen" is preparing to take out not a "potential shooter" but one clearly blasting away at innocents, "armed citizen" and I will be sharing the same target.
When it comes to justifiable homicide, identifying the correct target and making sure there is no collateral damage should you miss the said target is extremely important. What is really scary is the possibility of some innocent jumping out of a blind spot between you and the target just as you pull the trigger.
Recently read of an off-duty fireman who pulled a concealed pistol to make a "citizen's arrest" until police arrive of some dopey dude who entered a Walmart with an AR-15 wearing body armor shortly after a massacre at a Walmart.
If that fireman had just gunned that dopey dude down, his fate may have been placed in the hands of a grand jury.
Me dino is getting too old for such a high level of long term wait and see suspense.

My choice would be to hit the deck!

How can you tell the "Armed Citizen" isn't another potential shooter?