How did Adam Lanza go from being “just a normal little weird kid,” in his father’s words, to someone who “couldn’t get any more evil”?

Peter Lanza made the comments in a magazine story about his son, who slaughtered 20 children and six adults in a 2012 rampage at a Connecticut school. The elder Lanza had been estranged from his wife and had not seen his son for two years before the shooting.

In the wake of the massacre, investigators found many people knew Adam Lanza was deeply disturbed. But, like his father and the mother he also murdered, no one seemed to make the link between Adam Lanza’s mental illness and a propensity for violence – though there were signals of it.

Since the horror in Newtown, Conn., much has been said and written about gun control. Comparatively little attention has been paid to advancing our understanding of mental illness – and finding ways to stop the Adam Lanzas of the world before they kill.

Clearly, more needs to be done to diagnose and treat – or lock up – people like Adam Lanza.

We know that.

So why are we as a society not tackling the problem?