Being an outsider (Australian) I can tell you what our laws are like here. I know they have been explained but I will do it again.
http://en.wikipedia.org/wiki/Port_Arthur_massacre_(Australia)
In 1996 we had our own version of what you guys seem to be occurring far too often. Yes the guy had a mental disability and yes it was a huge reason why this happened in the first place. What did we do? We banned the sale of semi automatic weapons to the general public. We saw no reason for anyone to have large capacity magazines and the ability to keep spraying bullets as fast as you can. We took away the ability to modify a weapon you could buy over the counter and turn it fully automatic.
So what happened in Australia? We accepted it. We as a nation saw logic and reason. We saw that if we limit the opportunity for this to happen again to this extent then we won't have to mourn the loss of one of our own the same way. In Australia its illegal to own a weapon for self protection and you know what? We have very very little reason for that same reason.
What I see as part of the problem about American gun mind set - is the idea that if someone comes onto my property I can shoot them and preferably dead. I am not saying that you don't have the right to defend you or your family at all, what I have a problem with is the mind set that to protect myself I have to have a gun as a deterrent.
Do see a bad guy thinking oh they might have a gun so I won't break in and take what I want? Nope they do it anyway and the consequences will be what they will be.
Was the "right to bear arms" really meant to mean the right to own a gun no matter what? or was it meant to mean the right to take up arms and protect ourselves from a government or organisation that is attempting to take away the freedoms that you fought for in the Civil War?
In Australia we don't have a mind set that a gun will protect us, the UK is exactly the same. The police in England don't even carry a gun on the street, only special divisions within their police force are allowed to carry weapons. They have gun laws, they have private gun owners but they don't have this need or want to end up in the newspapers being displayed as some sort of twisted idol this is repeated again and again.
You might say that I have no idea what its like in the USA and therefore I can't comment. If I lived there I would need a gun to feel safe but that is 99% of the problem. The NRA and gun lobbies want to scare you into thinking your rights will be taken away if you have any restrictions on your gun laws. Why can't you guys have a sensible and rational discussion about the best way to prevent the severity of the problem?
The easiest thing to say is - mental health. Lets get rid of the loonies and this will never happen again but that's not the real answer is it. If you make it harder to get these weapons then it makes it harder to repeat. Proper background checks, guns that are designed not specifically to kill only people, perhaps smaller magazine capacities.
Just because the amendment exists doesn't mean its always right. Just because something was always done a particular way, doesn't mean its right.
The true definition of insanity is doing the same thing over and over and expecting a different result.