Both sides over-react when this kind of thing happens. Staunch anti-gun people go ape about banning all weapons (which will never happen imo) and the gun nuts launch into a campaign to arm everyone possibly related to the incident.
Although, I have to say that having a "gun free zone" is a little silly. It's almost a 'small' version of banning weapons. The law biding people that could have helped prevent the school shooting wouldn't have been allowed to have a weapon on them (this includes anyplace that serves alcohol or is a government property - such as the obvious, a courthouse, to the less obvious, a community college). It's like saying "If you commit a crime with a gun here you're in more trouble!" Like someone assaulting you with a gun is worried about being charged for having the gun in a gun free zone. Although I have to admit not being allowed to have them in a bar or courthouse is probably a very good idea. Schools and parks? Not so sure about that one (in Washington they recently started allowing firearms in state parks).
I have a fairly lengthy post I could put up that I had researched back in college and updated a couple years ago - information was taken from multiple sources and, imo, puts out a reasonably unbiased result. It shows that positive acts with guns far, far outweigh negatives with guns (i.e. how many deaths are prevented vs how many occur due to firearms) even when you are extremely conservative with the numbers. Assuming only a little under 4% of the median example of people who believe a criminal death (non-suicide) was prevented due to a firearm were actually correct you're still three times more likely to be saved by a firearm than be killed by someone with one.
For example, do you know that a child up to the age of 15 is three times more likely to be backed over in the driveway than die after finding an adults weapon and killing themselves? Or, that you are statistically three times more likely to drown in a pool than accidentally shoot yourself? And those are examples that are more favorable to the anti-gun side than many of the others that could be used.
Anyhow, my opinion since the early/mid 90's has been that guns need to be treated like cars. To own one you must take (and pass) a gun safety class, if you do something stupid with your gun or it is used negatively by someone else and you did not or do not report the gun stolen you are held responsible in one form or another (anything from a fine, to losing you gun rights, to jail time), guns would have titles that must be transferred when you buy/sell a gun (that would have to clear a licensing dept before you get it - i.e. background check that includes Criminal and Mental detail. If gun shows do not want to make people wait they can get some kind of on-site capacity to do this. Right now I could go sell my .45 at a gun show and no one would know. No record of the sale, I don't have to report it, no waiting period, etc. If it is used in a crime all I have to say is "Oh, yeah, I sold that gun years ago... Nope, no idea who the guy is anymore..." What's to stop a gun dealer (a legal one) from 'buying' his own guns (or have a friendly party do it) then re-sell them at a gun show?
Anyhow, as with far too many political debates the 'two sides' are so far off to one side that it gets ridiculous. I believe the country is far more centered than politicians/lobbies would have us believe.