I just have to add to that, how do you think the ani-gun people will handle this publicly?
Headlines reading something to the effect Pro gun rights failed to save lives?
That all the more would support their belief that guns should only be in the hands of police and government and not in the hands of a citizen.
I believe it would reflect worse than if no one there had a weapon!
Furthermore these questions should have been answered for anyone before you started carrying. Makes no since to walk into the world having doubts about what to do in a case like this.
Recognizing if the situation calls for your predetermined causes to use your weapon are different...this is something you should have already decided on.
If you ever have to use a firearm, you don't get to pick the scenario!