I have one 9 MM pistol for protection that I keep in my home. And I feel safer for having it. I have been through firearms training for marksmanship and safety. And I abide by the laws.
If you outlaw guns, only outlaws will have guns. They are curiously unwilling to follow the laws.
I am sure when a mentally ill, narcissistic malcontent decides to plan his exit from this world, he researches where he will do the shooting and alters his plan if he find out that the site is a "Gun Free Zone".
After all, one would not want to get in trouble for breaking the law!
(BTW, if a shooter really wanted to have a grater chance to have a longer time to shoot, would it be at a Gun Free Zone, or would it be at a place where you knew there would be those that carry a gun?)