In his Newtown, Conn., neighborhood, a woodsy hillside development where dog owners walk together and friends gather for sunsets, 20-year-old Adam Lanza stood apart.
"He wasn't the most social kid," said Jim McDade, a homeowner on Yogananda Street, where Nancy Lanza, his neighbor and Adam's mother, was found dead Friday.
Lanza, after shooting his mother, went on to Sandy Hook Elementary School, where he committed the second-worst mass shooting in U.S. history, taking the lives of 20 children, six adults and himself, according to law-enforcement officials.
Acquaintances described him as unknowable.
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Lanza couldn't socialize typically from the time he was young, said Louise Tambascio, owner of My Place, a Newtown pizza restaurant, and a friend of Nancy Lanza's for 12 years, in an interview last night.
Adam Lanza had Asperger's syndrome, she said, and was "very smart" with a high intelligence quotient.
He "couldn't deal with regular people," McDade said.
McDade's daughter, who was a year or two behind Lanza, also resides on the street where the Lanzas lived. McDade said Adam Lanza was quiet and reserved.
Lanza was "different" and "definitely a challenge," his aunt, Marsha Lanza of Crystal Lake, Ill., said.
Nancy Lanza and her former husband, Peter Lanza, were divorced in 2009.
The Associated Press identified Peter Lanza as a tax director and vice president for GE Energy Financial Services.
In Newtown, the Yogananda Street home of the Lanzas was cordoned off yesterday.
Ralph Strocchia, 17, who lives about a quarter-mile from there, recalled Adam Lanza as a high-school senior who rode the school bus when Strocchia was in his first year. The popular kids sat in the rear, Strocchia said, and Lanza wasn't among them.
"He didn't talk," Strocchia said in an interview.
Catherine Urso, a Newtown resident and piano teacher, said her son Nicholas went to Newtown High School with Lanza. She said she used to see Lanza dressed in a style favored by Goths, a subculture drawn to wearing all black and to music inspired by decay and despair.
Adam Lanza's brother, Ryan Lanza, 24, was questioned by authorities in Hoboken, N.J. Ryan Lanza told officers he hadn't been in touch with his brother since about 2010.
People with Asperger's syndrome have difficulty with social, emotional and communication skills, as well as unusual behaviors and interests, according to the U.S. Centers for Disease Control and Prevention.