I am sorry to learn about the losses suffered by the community of Virginia Tech. My first reaction is to blame America's gun culture. After all, American kids are bombarded with images of gunbattles, gunslingers, and the gung-ho shoot-from-the-hip attitude as portrayed in the popular media. If they face these kinds of images growing up, how can they not come to accept guns as a solution to right the wrongs they face? But obviously, most kids don't do this -- only the ones driven to madness do.
If my first reaction was to think of gun culture, my next thought was, how to curb it? There is a powerful segment of Americans who will strongly oppose any attempts to prevent ordinary citizens from buying guns. King George might be trying to break into their houses, after all. And just in general, removing rights from people just sounds ... queasy to me.
But there is another option -- compulsory weapons training. Make it compulsory for anyone who buys a gun to receive training to use the gun, and psychological evaluation to gauge the person's mental health. This way, everyone who buys a gun automatically deals with a barrage of people who train him to use the gun properly (keep the gun safety on and all that); make sure he knows the what he will be liable for if he shoots his gun and hurts someone; and evaluate his general state of mind and fitness to use the gun. Preferably, there would also be a written exam (consisting of technical questions e.g. on gun care, and also -- crucially -- psychologically loaded questions like `How would you feel about shooting someone in the head?' which would give some basis to gauge the person's mental stability and mindset) which he would need to pass to get the license for the gun. (How do you think Seung-hoi Cho would have answered a question like that? Obviously with a rational answer -- but questions like this allow psychiatrists to pick up clues about the person's mental processes.)
In this way, guns become another state-regulated item, just like poison and radioactive materials. You might be asking, what next, will we need to give an exam to keep knives in our kitchens? To be honest, I think guns are far more dangerous than knives, because they are long-range weaponry, fire rapidly, and on average, do far more damage to the human body than a knife does.
Looking at this from an economic perspective, the use of guns in society has negative externality-like effects on society. Society wants individuals to use less guns than the individual wants to. Therefore, society should impose a tax on the individual who wants to use guns to bring his demand for guns down to an socially acceptable level. This tax is in the form of the gun training and written exam, which the individual would of course have to pay for just like any other training/exam.
We live in a world where we have to retake tests like the IELTS every few years just to prove that we are still as proficient at English as we were three years ago. I don't see anything wrong with taking a test to prove that we are fit to own a gun. In fact, there is more reason to make this a periodic test, say every two years. This way, kids will think twice before going off to buy guns to make themselves feel bigger.