The young man who killed 20 children and six adults at a Connecticut elementary school Friday suffered from a condition where he could literally feel no pain, according to a faculty member at his old high school.
Richard Novia, the advisor for the tech club at Newton High, said that if Adam Lanza cut or hurt himself, "he would not know it or feel it."
Novia's words are the latest from a series of former acquaintances of Lanza's to paint him as bright but obviously troubled.
"Adam Lanza has been a weird kid since we were five years old," wrote a neighbor and former classmate Timothy Dalton on Twitter. "As horrible as this was, I can't say I am surprised."
"[Adam] was not connected with the other kids," said family friend Barbara Frey. A relative told ABC News that Adam was "obviously not well."
Mark Tambascio, another family friend, said he believed Lanza's mother, Nancy, had become increasingly concerned in the last few months about Lanza's emotional and behavioral issues. Lanza's parents divorced three years ago and his mother was left to deal Lanza alone.
"It was getting a little harder for her as time went on," he said.
Divorce records obtained by ABC News revealed that Nancy was to "make all decisions" with respect to her son, but only after consulting with Lanza's father. The settlement awarded Nancy approximately a quarter million dollars a year in alimony but the documents do not mention any behavioral or mental health problems related to Adam Lanza.
Kyle Kromberg, another former classmate, said that Lanza could not keep eye contact with anyone.
"He hated looking at your eyes for more than a couple seconds," Kromberg said. "He'd always look down at his papers or whatever he was doing."
A former babysitter, Ryan Kraft, said Nancy told him never to leave Adam alone -- "Never even to the bathroom or turn your back on him at any time."
On Friday morning, Lanza shot Nancy in the face at the home they shared in Newtown, and then drove her car to Sandy Hook Elementary School. Dressed in black combat gear, the 20-year-old broke a window at the school, which had recently had a new security system installed, and within minutes had shot and killed six adults and 20 schoolchildren between the ages of five and 10.
Police said Lanza used a Bushmaster semiautomatic assault-style rifle to kill the children before using a handgun to take his own life. Officials said the guns were likely legally purchased by Nancy.
Officials told ABC News that computers removed from Lanza's family home over the weekend provide important clues into Lanza's twisted thinking.