That is a hard question.
I do have a carry permit and would I have fired? It really depends on the situation. There is a fine line between self defense and taking the law into your own hands. If I was with my family or buy my self when that started happening in front of me, yes I would shoot in a heart beat, but If there was a clean way out for my family then I would take it and get them out.
A permit to carry a gun is just that. It is not a badge nor does it mean that a person carrying a gun “has” to get involved in gun fights. Does it happen, yes we do read about it when a person shoots another somewhere to save the lives of others, but understand this is still a very grey area in many states.
Some questions you might ask your self if you think this might happen and you have a gun.
If I shoot this person, am I going to shoot someone else? I saved the day by killing the shooter, but one of my rounds kill a 6month old baby behind him that I did not see. Can I live knowing that I killed a child?
Whenever you use a gun in self defense you will have to answer for it. It might be clear as to what happened and the local DA will not file charges. The again, if you stay and shoot the person, one of the question you will be asked and have to show (usually at the seine) how were YOU threatened/ Did YOU have a way out? Why did YOU take the law into your own hands?
If you start shooting, will others think you are part of the problem? Will you get shot by the other good person trying to stop the shooter?
Can you live with your self if you duck and run and many others are killed?
This is really not a question you can ask where there is a simple answer. It will be different for everyone you talk to. Most will say, I’ll shoot the guy”. Well they just might, but no plan works out the way you think when the lead is flying.
All you can really do is keep practicing with your gun, Think up shooting scenarios could happen at the places you frequent. Be aware of your surroundings at all times. Keep an eye on the quickest way out. Keep an eye on you family. Also it is very important that you are also a good witness for law enforcement. What were they wearing, color hair, close and stuff like that.
For me, I shoot with my carry about once a month. I pay extra for “frangible” ammunition that when it strikes something hard it breaks up into a fine power to help prevent ricochets.
This is not a perfect answer, because there is none. Everyone will respond as to there own abilities.