Crazy exists. It is an element in nature. The Sandy Hook massacre only proves this, to a horribly disgusting degree. Of course, after horrible tragedies like this, the morgue dancers come out in full force, misreporting, misinforming, and opinionating all over the place. During the initial chaos, I heard that two men (then two brothers, then just one of the brothers, but the wrong one) had opened fire at an elementary school where his girlfriend (then his mother) was a teacher (now they're saying he killed his mother in her house and stole her guns, so why the hell was he at the school?), killed her and an entire kindergarten class. He also killed his father, who would later release a statement about how sorry he was for his sons actions (since, no, he's apparently not dead).
Then there are the nannies, who think that that the man who illegally stole guns, illegally took those guns to a school, and illegally murdered 20 kids and 6 adults, could have possibly been stopped by just one more law.
We need to stop looking at motive. Crazy has no motive, no grand inspiration. If anyone's motive needs to be discussed, it should be that of the teacher who hid her classroom full of kids in the bathroom, said, "I just need you all to know that I love you very much," before sacrificing herself to this lunatic. I want to know what her motive was, what drove her, and how we as a society can create more of her.
We cannot legislate a change in human evolution. When legislation is used to try and combat human insanity, often times, the most dangerously insane people control the legislation. Crazy will continue to exist, laws and regulations be damned.
We could look at the warning signs, but according to everyone who knew this guy, he was a walking red-flag. I don't bring this up to say "nobody tried to help him," but to say, "some people are beyond help." I don't think there is anything anyone could have done to prevent this., aside from being lucky and quick enough to shoot him first.
I don't think that these tragedies can be avoided. It's part of our earthly experience. The only thing we can do is arm ourselves and be vigilant.