Exactly.
Furthermore, if you don't POSSESS a gun you can't FIRE it.
Unless you know of a foolproof system that can read someone's hearts and minds, and therefor find a way to make sure the "evil-doers" cannot own guns, your post is actually a good argument for banning guns altogether.
You see, practically ANYONE in the US can own a gun. When you consider the human capacity for evil, that means there are a HUGE number of Columbines and Sandy Hooks just waiting to happen.
I also notice your earlier comment about "we would never use our guns for hurting anyone. We just keep them for the sick assholes etc to protect our children". So....if someone breaks into your home, you would point the gun (unloaded) and have a little "bang" flag pop out? You would shoot the intruder....AFAIK, if you shoot them, they are going to be hurt. In fact, your guns ARE for hurting people.
The biggest problem I can see is that there are a core group of US society that feel their right to own a gun is more important than just about anything else in the world. When you add that to the ridiculously high number of gun related deaths in the US, you don't have to be Einstein to figure out where the issues lay, and who is responsible.
As an aside, this Lanza woman is partly to blame for her son's actions. It appears that she actively encouraged him to use guns and had "family outings" to the gun range. IMO, that's the same as taking the family to a "bayonet range" where they can learn to kill people with sharp objects. You don't have to delve too far into the shooter's past to see why he was so f'ed up.
If the US wants to rid themselves of these massacres, they need to examine what it is about their way of life that drives people, particularly young people, to be so enraged and angry at the world that they feel innocent people need to die. My research over the years has led me to believe that in the "land of the free", one's amount of freedom is directly proportional to one's wealth and/or privilege. If you don't fit the mould, especially in the conservative religious areas, you are pretty much worthless and tossed into the waste basket. A whole lot of mentally ill people are left roaming the streets when they should be in care....but they cannot afford it, so tough luck.
I'll wager you one thing. The minute a federal politician, or other wealthy powerful citizen loses a child in one of these massacres, you'll see swift action like you've never seen before. The way things stand, the gun lobby have too much power, and the average American too little.
I'll just re-iterate my main point. If you don't have a gun, you can't fire it, and you can't shoot dozens of people. Not only do you need to deal with the guns, you need to deal with the people possessing them, and the fastest and quickest way to make a start is a gun amnesty/recall.