Ditto. I’ve been in a lot of Waffle Houses where the shooter would have been met with a hail of gunfire, and would up with more holes than a block of Swiss. I kid you not.
Perhaps, especially if the customers had been combat trained/experienced. However, I recently had some very realistic training in how to respond to a situation like this and it is incredibly hard to overcome the freeze response. I read of one survivor who said something like, "My heart was pounding but my body was stuck."
OTOH, Shaw did just what our trainer recommended - even for kids in a classroom at a school shooting: rush the perp. The only "training" most of these perps have had is playing video games. Making noise, throwing things, rushing him is going to distract/disorient him. You have a much better chance of survival than the duck & cover strategy. But it does mean overcoming the basic mammalian freeze response.