This kind of thing is sickening...this is an individual who does not need to be on the planet any longer, nor contribute to the gene pool.
The sad part about these kind of acts is that there is really not a hell of a lot you can do to stop it. A lone assailant, with tremendous firepower, can do an awful amount of damage before he/she is stopped. Just look at the Gabriel Giffords situation for another example of some extremeist, acting alone, filled with hate for this or that reason. And I'm pretty sure I know you can carry firearms in Arizona with relative impunity, and can carry concealed with a permit. That fact did not deter that individual. When you get some nutcase like this taking action, it all happens so fast, a lot of the damage is done before people know what's happening, or can react.
Unfortunately, I don't see this kind of random act stopping any time soon.