He was a loner, a 20-year-old whom Newtown High School classmates remembered as a skinny, shaggy-haired boy "who never really talked at all" and who stayed tight to the corridor walls when he walked, often clutching his laptop.
There was a common refrain among acquaintances of Adam Lanza: I knew of him but I didn't know him.
Lanza kept to himself. Over several bloody minutes Friday morning, armed with a rifle, Lanza emerged from his shell long enough to destroy the lives of 20 first-graders and six adults at Sandy Hook Elementary School. He'd gone to the school as a youth, a former classmate said.
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Newtown, CT, USA
On Friday morning, he drove to the school after killing his mother, Nancy Lanza, 52, in herhome2 miles away on Yogananda Street, law enforcement sources said. She was still in bed when he shot her, the sources said.
Adam Lanza had lived with his mother in the 4,000-square-foot, $700,000 house. His parents were divorced in 2009.
He had two bedrooms that were clean and orderly when law officers swept into the house after the shootings Friday morning. Lanza apparently lived in one of the rooms and kept his computer gear and other items in the other one, the sources said. Law officers found evidence that Adam Lanza played graphically violent video games, the sources said.
Lanza was estranged from his brother, Ryan Lanza, 24, and hadn't talked to his father since 2010, according to people who have known the family. Ryan, a graduate of Quinnipiac University in Hamden, works for the financial firm Ernst &Young and lives in an apartment in Hoboken, N.J.
Marsha Lanza, Adam Lanza's aunt, said it was her understanding that Nancy Lanza kept three guns in the home.
"Nancy was meticulous," Marsha Lanza told reporters outside her home in Crystal Lake, northwest of Chicago. "She would never leave the guns out."
Marsha Lanza called Nancy Lanza "self-reliant."
"The only reason she would have guns," Marsha Lanza said, "was for self-defense."
Two law enforcement sources said the murder weapon was one of those guns, a semiautomatic rifle. The others were a pair of semiautomatic pistols.
But why Adam Lanza embarked on the deadliest rampage at an elementary school in U.S. history is an open question. Law officers have a sense of his home life, but they have yet to nail down a motive.
The sources said investigators believe Adam Lanza's isolation and social awkwardness were consistent with Asperger's syndrome. Asperger's is a disorder that is part of the autism spectrum. It is marked by difficulty with social interaction. Many with Asperger's are otherwise high-functioning people. There is no pre-disposition toward violence, experts said.
"It's very important for people to know that there is absolutely no correlation between the diagnosis of Asperger's syndrome and a predilection toward violent behavior,'' said Dr. Harold Schwartz, chief psychiatrist at the Institute of Living in Hartford.
The reasons someone may suddenly commit unfathomable violence are, at best, elusive.
"Frankly, it is the kind of question no one can answer, but there are patterns,'' said Schwartz. "There are 'grievance collectors,' people who walk around feeling deeply aggrieved and harboring enormous resentments. But they don't have the skill to address what they are feeling in any productive way.
"They can act out, and through some fantastic thinking, believe that somehow the world will understand the depth of their pain when others see what they have done,'' said Schwartz.
Adam Lanza's relatives were at a loss to explain his actions.
"Like you, we want to know why," said Marsha Lanza. "My heart goes out to all the families."