"The mentally ill have rights!" said the "advocates" back in the 1960's and 1970's. Judges agreed, and the doors of the asylums began opening, leading to the homelessness problem.
Part of the problem is the creeping crud of Relativism: one can easily find all sorts of essays from professors and leftist advocates back then for this newly discovered set of "victims" about how the mentally ill are not all that different, that they have just another way of looking at the world, and maybe...just maybe!...they are saner than the people locking them up! See e.g. the attitude in the movie One Flew Over the Cuckoos Nest.
It was typical that instances of abuse in mental hospitals - which was not the norm - could be used to empty forth many supposedly non-violent patients.
But note! Lanza was never identified as schizoid, although one can easily assume he was obeying certain hallucinated voices as he went on his spree. Protected by his (possibly lunatic yet still functional) mother, there was no way he could have been diagnosed and treated. And even if he had been diagnosed, he would not have been institutionalized without cause, and schizophrenics are notorious for not wanting to be medicated.
And so what do we do as Conservatives?
The danger here is falling prey to wanting to control EVERY possibility in Life, which will lead only to the tail wagging the dog of society. Putting every one into a strait-jacket - real or metaphorical - might work, except for those who can pop their shoulders and get out...and somebody will!
Life is not a puppet show: everyone has free will, even the mentally ill. If someone decides to swing an ax at your head, no angel will come down to stop the ax, so that the freedom to commit Good can exist. And this is so, because unless there is freedom to commit Evil, there can be no freedom to commit Good.
The presence of Evil is always a spur for the rest of us to create Good.
Leftists want control of every aspect in Life because they have no or very little higher FAITH in anything but their own ideology. Having driven God or any idea of divinity out of Life, they are left with playing God themselves, and playing Him badly, and will create more insanity as they try to control Life in a futile, quixotic quest.
Conservatives will respond with Faith and wisdom, not with more government control, which is as doomed to fail to prevent such a lunatic as the present control mechanisms. A Conservative will wisely refuse to equate mental illness as another way of looking at the world, and will work to reverse the idiocy in our society accepting such a view.