This is all too familiar here in my neck of the woods, but I personally do not see why we must go to the extreme every time this occurs.
Gun 'control' is myth, and only affects the honest people who are scared and are trying to protect themselves (wrongly or not, aside) from the individuals who got them by ill means in the first place. If we ban guns, we reduce sales at the local outdoor supply store, upset an entire community (hunters), reduce direct funding for DoWs and the like, and put undo pressure on the military every time a murder occurs (since thet would be the only 'legal' non-police unit to carry). If someone wants something, they can get it. It isn't a case of what you have so much as why you have it (yes, I grew up target shooting and respect was ingrained in the process for me, I was also a dependent).
In this case, the shooter was deeply troubled (from I know anyway), and is not the type of person that arms should be sold to, so it wasn't a failure of policy so much as a failure of procedure, or ease of access in the home (regulation of shells is also lacking, though...anyone see bowling for columbine?). It is also troubling that mental illness is often seen as an embarrassment and something to hide, so the burden on a family is great, and society, in general here in the US is lacking, as it is the expectation is put on the family to deal with it, not the community (my perceptions may be off, but this is the way I see it).
I also have a big issue with this type of thing because it puts a greater amount of focus behind preventing it next time rather than helping the families and their communities get past the present. Put today first, until tomorrow is able to have your full attention. By the loud outcry of gun control, mental illness, school security, and God (not touching this one in such an informal way, but I do support him and know he's got a special place for the 20 children), we lose sight of the fact that parents lost their children, more lost their personal sense of peace in their own hometown. Lastly, this will go down as 'another school shooting,' and with such a polarizing topic, it will only fuel the fire next time, because this issue will not resolve (unfortunately, we will have it happen again, for reasons I just stated, and because there are only 2 kinds of people in the world: people and people trying to do the right thing.)
Good we can talk about it though, discussion is great, especially when we disagree (I don't want to argue about it, so let's talk). I can't imagine what those parents are going through and they will never have a good Winter Holiday (staying PC here) again. I am also saddened by the fact that they will never get a sense of justice from this, be it the chance to forgive the shooter, or watching the legal system work for a change. I can't even begin to put myself in their place and really don't want to.