When you look at pictures of Adam Lanza, you know there was something really wrong with him that was not caused by an absent father or SSRIs or psychiatrists. Even his skull was misshaped. He must have had some kind of inborn problem. People can be born with birth defects in the heart or stomach or kidney, so no doubt they can be born with defects in the brain as well.
Truth be told, I’ve been through a LOT and Lanza had choices to make either way. He was already way into the culture of death and he was WAY too into living a life where he was an empty vessel waiting to be use by a demon.
I sincerely think that he was possessed (does not excuse what he did to those children by the way since there is choice in choosing to do the work of the devil) and evil was acting through him.