It would be interesting to have the actual statistics on how often this happens. And one could probably actually compile meaningful numbers for the statistics, which says quite a lot in itself. I don't doubt that armed people can help fight off other armed people especially if they're well trained, I still doubt the NRA position that having more armed people would help in many or most mass shooting situations. But anyway, there's not much point in us raking over this one again.
Meanwhile, a terrorist attack has happened in Bangladesh leaving 20 dead, thought to be done by Islamists/ISIS; though they're also feeling pressure on the ground, as apparently the US just took out two more senior commanders of theirs in Iraq with an air strike.