1. If Adam Lanza had no easy access to guns, NOBODY would have been killed.
Whether he had Aspergers, was mentally ill, had treatment or no treatment, was intelligent or not, the bottom line is that he had easy access to guns and thus was able to go out and slaughter a bunch of people.
The problem is it isn't apples and apples. I think you could get much more support for mental health care issues. In fact, under the general welfare clause you could advance policy for such, meaning providing for mental health care under the guise of protecting the citizens could be seen as constitutionally consistent. Guns, not as easy as you'd be going 'against' the constitution (although not sure what part of well regulated some miss).
A really phucked up person who wants to do damage will find a way to do it. Take guns out of Adam Lanza's hands and he may have taken his car and run over 20-30 kids during recess one day. Dead is still dead.