Without a time machine, we have absolutely no way to know if they did the right thing. Maybe if they had chosen the other path, they'd all be dead now. We'll never know.
Of course. But our reason for discussing this stuff in S&T is to attempt to distill what the
likely realities of the situation were, without the 'fog of battle' clouding our judgment -- to discern what worked, what didn't work, what might have worked better, what was sheer luck and shouldn't be counted on, and how things might have changed the game -- so that we may learn a bit more about how WE should react to some similar situation in a way that
might work best to preserve our own lives or those of loved ones.
In this case, we have a decently clear picture of the course of events, and a pretty good account of what was said.
From those facts, we can make some pretty strong assumptions about the intents of those involved and the possible outcomes that different choices might have produced.
Would reacting to the drawn gun by backing off and standing aside caused MORE people to die? Or would it have put fewer lives at immediate risk?
Would allowing him to leave have ended in mass murder and a police standoff? Or would it have ended with the perpetrator running out the door, leaving the property, being identified on security tapes and apprehended later by the police in a controlled and well-planned arrest?
Would one false move -- one unlucky twist of a finger -- in the counterattack have left one or more employees dead? Would that killing have prompted a more violent and desperate escape? Would that killing have pushed the perpetrator to greater and more violent acts of desperation knowing that he was now wanted on multiple manslaughter charges?
Just thowing up our hands and saying, "oh, we'll never know," doesn't indicate that we're benefiting from the analysis, here. If we can't learn from this, why even discuss it? We aren't here for entertainment or to cheer on the good guy and boo the bad guys. This is supposed to be a learning experience.
Up at West Point, they don't study Waterloo because they're all Wellington fans and hate Napoleon. And they're not just "really into" history. There are lessons to be learned that could be applicable in their lives in the future.