His mother knew he had problems and she wasn't a survialist according to this report

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Adam Lanza, 20, was described as a “recluse’’ by his mother to friends. Nancy Lanza divorced her husband, General Electric executive Peter Lanza, in 2009, and he left her their spacious 3,100-square foot home in Newtown where Adam spent the majority of his time.

 “He was clearly a troubled child,’’ said Hanoman, who was the only one of the four friends to have met Adam. “We know that he had Asperger’s. Nancy mentioned that to me several times. He was very calm, very withdrawn, much like most kids with Asperger’s are. He was typical in that regard.’’

 “Sometimes he would isolate himself, things like that,’’ Adriani said. “She was very conscious of how she would react to him. For an example, one time he was ill, and he just didn’t want her in the room, so she stayed outside of his bedroom all night on the carpet, and he periodically would say, ‘Are you there? Are you there?’ And she’d always say, ‘Yes I’m here.’ So he wanted her there to some degree, but not in his exact, immediate space.’’

 She was definitely not a survivalist,” Bergquist said. “Shooting was one of her hobbies. It wasn’t her main hobby. She loved the arts, culture. She loved the finer things in life. She loved to go to Red Sox games, and that’s the Nancy I knew.’’

 “She took up target shooting a few years ago,’’ Tambascio told NBC News. “She was a single mom raising two boys living alone in a house that’s close to the woods. I don’t see anything odd.’’

 Andrew Solomon, the author of "Far from the Tree,'' a book about parents dealing with children with exceptional conditions ranging from disabilities to mental illness to prodigal talents, told Guthrie that people often look to the parents for answers in situations like the Connecticut shooting. In the research for his book, Solomon spoke with the parents of Columbine shooter Dylan Klebold. 

 "The first thing is that I think that we always expect that the family will provide an explanation of why,'' Solomon said. "We think that if we understand the family, we'll know why it happened. But these illnesses strike people as randomly as cancer or any other illness. So I think the family can't be held responsible for it, at least not from the evidence so far. 

 "This was an act of rage and violence, but it was also an act of extreme depression. Murder-suicides, everyone always focuses on the murder piece, which is the more upsetting piece, but if you don't look at the suicide, you'll never figure out what it is that drives people this way. Sometimes the parents know and they can't do anything, and sometimes the kids are very secretive, and we don't know yet which this is (in the Connecticut case)."