The real problem isn't the "loonies". They might have a shooting spree every few years, but the vast majority of gun deaths in the U.S. have nothing to do with shooting rampages. So far as I know most gun injuries and deaths in the U.S. are accidental. Basically people playing or fiddling with guns. This guy killed 20 children, well around 100 children on average are killed in the U.S. each year due to accidents involving guns. So where's the outrage over that?
I think the biggest problem is that people in the U.S. have no respect or appreciation for guns. When you don't even have to register your weapons, or pass some sort of proficiency or safety test - then why would anybody have any respect for the weapons? Imagine what the roads would be like if nobody had to register their car or take a driver's test. Yeah, pretty awful. Yet we're cavalier towards killing machines, and the NRA spends millions of dollars to defend gun owners "rights" to be stupid and careless.
I'd also add that the kind of rampages we see, like with Virginia Tech, and here in Connecticut, would not be possible with a shotgun or a normal revolver. You just cannot kill that many people that quickly unless you had them all lined up. We need to put our heads on straight here instead of sticking our heads in the sand. While some guns have legitimate uses, some do not, and should not be available to the general public (let alone a general public with no appreciation for the safety of others or themselves).