Getting people to understand the simplistic concept of how not having easy access to guns - and not having guns as an integral part of your culture - will prevent a LOT more tragedies than it will create, is harder than one would think. Even if it means saving ten times more lives, people will prefer to be able to defend themselves with guns because there's a chance they'll get attacked. Well, people without much of a brain or without much care for the majority.
Basically, people are not very bright - and most have a hard time keeping more than a handful of factors in mind when they form opinions. For instance, a lot of people think that because some people will go through the effort of getting hold of a gun illegally - that means everyone will have access to one when they break down and go on an assault like this. Even a simpleton would understand that's not the case - and yet it's one of the most common arguments against stricter gun control.
However, I know that stricter gun control will arrive in the US - it's just a matter of time. When that happens, and not having a gun becomes part of the culture - everything will be much easier to comprehend. That said, the fools arguing against it will not be able to acknowledge this as the reason for fewer gun-related crimes. Luckily, that's irrelevant - because lives will be saved and that's all that matters.
But it will take time.
So, a lot of people will die needlessly - and people will proudly bash their chest in ignorance of even the simplest and most obvious ways to prevent a lot of cases like this. All cases? No - but a LOT.