Mass murderer Adam Lanza was just nine years old when his mother Nancy gave chilling advice to his babysitter: "Don't turn your back on him!"
Ryan Kraft grew up just two doors from the Lanza family, and babysat for little Adam.
Kraft told INSIDE EDITION, "Adam always struck me as a really introverted kid. He was really, really quiet. Whenever we were doing something, whether it was buidling Legos, or playing video games, he was really focused on it. It was like he was in his own world."
Kraft will never forget the mom's parting advice before she left the house.
Somehow, that child grew to become the mass murderer who inflicted immeasurable pain upon an idyllic small town in Connecticut—though incredibly, he could feel no pain himself.
A friend of Adam's mom says Adam tried to hurt himself by "burning himself with a lighter, in the ankles or arms or something. It was like he was trying to feel something." (Source: New York Daily News)
Why would anyone do that?
Dr. Harold Koplewicz, President of the Child Mind Institute told INSIDE EDITION, "There are many teenagers who complain they don't feel anything. By physically hurting themselves, either with cutting or with burning, they feel more alive. This is clearly a symptom of psychiatric disorder."
Adam belonged to the tech club at Newton High, a somber face amid many smiling faces. He was reportedly badly hurt when his parents' marriage fell apart, and he'd been estranged from his older brother Ryan since 2010.
But this same troubled boy took college classes at Western Connecticut State University when he was just 16 and did well in computer and history classes.
Adam suffered from Asperger's Syndrome, a mild form of Autism. But experts say there is no connection between that condition and violence.
Nancy Alspaugh-Jackson is Executive Director of Act Today, an Autism Advocacy group. Alspaugh-Jackson told INSIDE EDITION, "It's much more common for children with Asperger's to be on the receiving end of violence than on the giving end of violent behavior."
So what made Adam Lanza do what he did? We may never know.