The way I look at it, if a murderous lunatic has their heart set on indiscriminately killing people, all the gun control in the world ain't going to stop them.  They'll make a bomb, use a car, sh*t you can run through a mall with a samurai sword and kill loads of people before getting gunned down by the authorities or gun-wielding citizen.

I tend to think there really isn't much ya can do about the lone lunatic, not without unintended consequences making all of the society the lesser for it.  The police state has grown in leaps and bounds over the last 50-60 years, killing each other remains.

And like Slayer said, it's very very rare (thank goodness).  Never a good idea to react in haste to such rare, though unimaginably horrible, tragedies in ways that effect us all, all the time.  9/11 shoulda taught us that.