A lot of people have this strange idea that they instantly become Chuck Norris when danger rears its ugly head. In extreme danger situations, instinct to survive takes over unless you have been trained differently. Some people did attack the gunman.
That’s why regular range time is a must. ;>)
Can you cite instances?
Some did attack? Do you have a source for this. I have actually read the opposite; in fact, this article notes that there was no evidence of anyone fighting back.