Except that 6.5 million AR-15's were sold when a rumor was started about gun control. That says that the ownership of this exact firearm design is far more popular among Millenials than prior generations.
Nor will restricting access to new AR-15s reduce the rate of mental illness. I'm not sure what will bring about such a reduction, but once the desire to kill exists, I for one want these sick people fixated on relatively harmless small arms. The most approprriate example of the kind of thing that can happen otherwise was 9/11, which was just shy of 3000 casualties. That's the sort of "outside the box" thinking about killing that we want to avoid.
You seem to be the one fixated upon an inappropriate response. Not to mention that gun violence has been on an uninteruppted decline for 25 years. Look back over your own response to a non-issue.
I am suggesting that we address the mental illness. In the case of Cruz I suggested that his mental condition possibly resulted from Fetal Alcohol Syndrome, and you led a chorus of people to suggest that I have made a rascist remark. Yet the visible markers for this disease are in plain sight in the published photographs, in distorted facial features and in under-developed ear cartilage.

Why is it that you are so intolerant of the suggestion that there might be an actual clinical basis for his mental disfunction, because he was exposed to toxic alcohol in the womb? It does not excuse what he did, and if true, would have been a legitimate reason to deny ready access to firearms to somebody who likely does not possess the ability to reason out more deadly alternatives.

Do you even want a solution? Are you going to overlook or ignore the possibility that no solution may be necessary? Remember that media manipulation is in play here. Those who specialize in manipulating others, who have made careers out of that very thing, have been inside your head. Decide if you care and whether or not you will make the effort to reason through such manipulation.