All deaths could have been avoided if it had been known that A. a person with intent was B. in possession of a gun and stopped before entering the target space. What does it take to know these factors? Nearly supernatural powers or supernatural powers. Powers that should have been in possession of the 1st target ie. his mother.
But his mother did not have those powers. Not only that but she was the gun owner which means that gun ownership does not guarentee survival. Who has supernatural powers to know both person of intent and 'in possession'? Well God for one. So where was God? The bible says God is omipresent. So for reason or reasons we do not understand God stood by and let those people in (all mass shootings) die without so much as intervening. Then what is God's mission if it is not to save lives? Suppose for a moment an atheist is correct that God does not exist. Then non-god has non-powers to not supernaturally intevene, people die and that's that and the suidcidal shooter escapes justice. Is the universe unfair in both instances? Who are we to say we are just dust?
Do you follow me? So let's say that we love justice and boy we sure wish that shooter was alive so we could drag him through town behind our trailer hitch for killing those children. But he isn't he killed himself and escaped justice (or the confrontation of a hopeless court case that would lead to his conviction). He judged himself and carried out the execution is that fair? Not entirely because we like justice and having people answerable.
Now let's suppose that God exists and he loves justice. The bible says our God is a Just god, cursing those to infinity those who curse Him and loving to infinity those who love Him. If the children then are loved by God, and they are because the Bible tells us so, then they are in His presence. What of their murderer? You answer that.
So if the two ways of reducing your chances of death by mass-murdering gunfire are distance and removal of intent wouldn't it be in our best interest to promote beliefe in God? That no matter how you try to hide you will be punished for your crimes for infinity? Infinity is longer than life in prison without chances of parole. Infinity is forever and ever and ever and when we are done with all the forevers then Amen!
Lastly, then there is a 3rd way to survive mass murdering gunfire and that is to be in possession of recognizable deadly force, such as a handgun. Being threatening with a gun or firing a gun in defense has greater than 0% probability of reducing or avoiding deaths by mass murdering gunfire. Ann Coulter's statistics prove this in her editorial piece titled "We Know How to Stop School Shootings". So in conclusion I would say that promoting belief in God as inescapable avenger and deliverer of justice and allowing the possession of deadly force, combined, should reduce death by mass murdering gunfire by a drastic amount.