I think it's a problem that occurs because we live in such safe, controlled environments. I don't mean "controlled" in the Conspiracy Theorist way, I mean "controlled" as in society itself functions in a way that deters randomness of that nature.
The problem with this is, despite all of our "civilisation" these sort of events do happen. If someone wants to go on a rampage and slaughter a whole bunch of people, there's really no effective response. They're going to kill a lot of people. It's really unavoidable (unless you prevent the attack before it happens).
Sure, you could have "mass shooting" drills in schools and work places, but what's the point? how often do they happen? The USSS did a comprehensive study of shootings after Columbine and concluded there was absolutely no common factor amongst shooters and their methodology. Anyone could be a shooter, and the shooting could unfold in any way.
You simply cannot plan for that sort of instance.
It's quite simply a fact of life that Americans have to live with, that as long as they continue to allow free access to firearms, and as long as the youth are conditioned to kill, and as long as the youth are desensitised to violence, and as long as there is a culture of violence and social segregation in American schools, school shootings will continue to occur.
-Gumboot