Now Adam Lanza is suspected of killing his mother and then gunning down more than two dozen people, 20 of them children, at a Connecticut grade school before taking his own life.
The 20-year-old may have suffered from a personality disorder, law enforcement officials said.
Investigators were trying to learn as much as possible about Lanza and questioned his older brother, who is not believed to have any involvement in the rampage.
Lanza shot his mother at their home before driving her car to Sandy Hook Elementary School and - armed with at least two handguns - carried out the massacre, officials said.
A third weapon, a .223-caliber rifle, was found in the car, and more guns were recovered during the investigation.
So far, authorities have not spoken publicly of any possible motive. They found no note or manifesto, and Lanza had no criminal history.
Witnesses said the shooter didn't utter a word.
Lanza's aunt said her nephew was raised by kind, nurturing parents who would not have hesitated to seek mental help for him if he needed it.
Marsha Lanza, of Crystal Lake, Ill., said she was close with Adam Lanza's mother and sent her a Facebook message Friday morning asking how she was doing. Nancy Lanza never responded.
Marsha Lanza described Nancy Lanza as a good mother and kind-hearted.
If her son had needed counseling, "Nancy wasn't one to deny reality," she told The Associated Press late Friday.
Marsha Lanza said her husband saw Adam as recently as June and recalled nothing out of the ordinary about him.
Catherine Urso, who was attending a vigil Friday evening in Newtown, Conn., said her college-age son knew the killer and remembered him for his alternative style.
"He just said he was very thin, very remote and was one of the goths," she said.
Adam Lanza belonged to a technology club at Newtown High School that held "LAN parties" - short for local area network - in which students would gather at a member's home, hook up their computers into a small network and play games.
Gloria Milas, whose son Joshua was in the club with Lanza, said Nancy Lanza hosted one of the parties.
She recalled a school meeting in 2008 organized by the gunman's mother to try to save the job of the club's adviser. At the meeting, Milas said, Adam Lanza's brother Ryan said a few words in support of the adviser, who he said had taken his brother under his wing.
"My brother has always been a nerd," Ryan Lanza said then, according to Milas. "He still wears a pocket protector."
Joshua Milas, who graduated from Newtown High School in 2009, said Adam Lanza was generally a happy person but that he hadn't seen him in a few years.
"We would hang out, and he was a good kid. He was smart," Joshua Milas said. "He was probably one of the smartest kids I know. He was probably a genius."
Lanza and his mother, Nancy, lived in a well-to-do part of Newtown, a prosperous community of 27,000 people about 60 miles northeast of New York City.
A grandmother of the suspect - who is also the mother of Nancy Lanza - was too distraught to speak when reached by phone at her home in Brooksville, Fla.
"I just don't know, and I can't make a comment right now," Dorothy Hanson, 78, said in a shaky voice as she started to cry. She said she hadn't heard anything official about her daughter and grandsons. She declined to comment further and hung up.
A law enforcement official speaking on condition of anonymity said investigators believe Lanza attended the school several years ago but appeared to have no recent connection to the place.
At least one parent said Lanza's mother was a substitute teacher there. But her name did not appear on a staff list. And the law enforcement official said investigators were unable to establish any connection so far between her and the school.
Adam Lanza's older brother, now 24 and living in Hoboken, N.J., was being questioned, a law enforcement official said. He told authorities that his brother was believed to suffer from a personality disorder, the official said, speaking on condition of anonymity because he was not authorized to speak on the record about the unfolding investigation.
The official did not elaborate, and it was unclear exactly what type of disorder he might have had.
Ryan Lanza had been extremely cooperative and was not under arrest or in custody, but investigators were still searching his computers and phone records. Ryan Lanza told law enforcement he had not been in touch with his brother since about 2010.
Brett Wilshe, a friend of Ryan Lanza's, said he sent him a Facebook message Friday asking what was going on and if he was OK. According to Wilshe, Lanza's reply was something along the lines of: "It was my brother. I think my mother is dead. Oh my God."
Adam Lanza attended Newtown High School, and several local news clippings from recent years mention his name among the school's honor roll students.
Lanza's parents filed for divorce in 2008, according to court records. His father, Peter Lanza, lives in Stamford, Conn., according to public records, and he reportedly works as a tax director for General Electric.
An official who spoke on condition of anonymity said it was not clear that Adam Lanza had a job, and there was no indication of law enforcement interviews or search warrants at a place of business.
A neighbor in Newtown, Rhonda Cullens, said she knew Nancy Lanza from monthly get-togethers the neighborhood women had a few years back for games of bunco, a dice game.
"She was a very nice lady," Cullens said. "She was just like all the rest of us in the neighborhood, just a regular person."
Cullens recalled that Lanza liked to garden and to make her house look nice for the holidays. Lanza joked, though, that no one noticed because the house was out of view, up a hill, she said.
Sandeep Kapur, who lives two doors down from the Lanza family in Newtown, said he did not know them and was unaware of any disturbances at the Lanza house in the three years that he and his family have been in the neighborhood.
He described the area as a subdivision of well-tended, 15-year-old homes on lots of an acre or more, where many people work at companies like General Electric, Pepsi and IBM. Some are doctors, and his next-door neighbor is a bank CEO, said Kapur, a project manager at an information technology firm.
"The neighborhood's great. We have young kids, and they have lots of friends," he said. "If you drive past this neighborhood, it gives you a really warm feeling."
Keyser reported from Chicago. Contributing to this report were Associated Press writers Adam Geller and Matt Apuzzo in Newtown, Conn.; Dave Collins in Hartford, Conn.; Michael Tarm in Crystal Lake, Ill.; and Michael Rubinkam.
CORRECTION: In some versions of a story Dec. 14 and 15 about the suspect in a school shooting in Connecticut, The Associated Press erroneously reported a comment by Gloria Milas about who hosted a high school technology club party. She said the suspect's mother was the host, not herself.
SOUTHBURY, Conn. — At Newtown High School, Adam Lanza had trouble relating to fellow students and teachers, but that was only part of his problem. He seemed not to feel physical or emotional pain in the same way as classmates.
Richard Novia, the school district’s head of security until 2008, who also served as adviser for the school technology club, said Lanza clearly “had some disabilities.”
“If that boy would’ve burned himself, he would not have known it or felt it physically,” Novia told The Associated Press in a phone interview. “It was my job to pay close attention to that.”
Novia was responsible for monitoring students as they used soldering tools and other potentially dangerous electrical equipment.
He recalled meeting with school guidance counselors, administrators and with the boy’s mother, Nancy Lanza, to understand his problems and find ways to ensure his safety. But there were others crises only a mother could solve.
“He would have an episode, and she’d have to return or come to the high school and deal with it,” Novia said, describing how the young man would sometimes withdraw completely “from whatever he was supposed to be doing,” whether it was sitting in class or reading a book.
Adam Lanza “could take flight, which I think was the big issue, and it wasn’t a rebellious or defiant thing,” Novia said. “It was withdrawal.”
Authorities on Saturday continued a wide-ranging investigating into the second-deadliest school shooting in U.S. history, trying to understand what led the young man to kill his mother in their home and then slaughter 26 children and adults at a Connecticut elementary school before taking his own life.
Back in their teenage years, Adam and his older brother, Ryan, were both members of the tech club, which offered students a chance to work on computers, videotape school events and produce public-access broadcasts.
It was popular among socially awkward students. But Adam, while clearly smart, had problems that went beyond an adolescent lack of social skills, Novia said.
“You had yourself a very scared young boy, who was very nervous around people he could trust or he refused to speak with,” Novia said.
The club provided a setting for students to build lasting friendships. But while other members were acquainted with Adam, none was close to him.
“Have you found his best friend? Have you found a friend?” Novia asked. “You’re not going to. He was a loner.”
Adam was not physically bullied, although he may have been teased, Novia said.
The club gave the boy a place where he could be more at ease and indulge his interest in computers. His anxieties appeared to ease somewhat, but they never disappeared. When people approached him in the hallways, he would press himself against the wall or walk in a different direction, clutching tight to his black case.
“The behavior would be more like an 8-year-old who refuses to give up his teddy bear,” Novia said. “What you knew with Adam is it was a possession. It was not a possession to be put at risk.”
Even so, Novia said, his primary concern was that Adam might become a target for abuse by his fellow students, not that he might become a threat.
“Somewhere along in the last four years, there were significant changes that led to what has happened,” Novia said. “I could never have foreseen him doing that.”
Jim McDade, who lives a few houses from where Nancy Lanza was slain, said his family became acquainted with the two brothers and their mother because their children were about the same ages and rode the school bus together.
“There was certainly no indication of anything unusual that lets you think that a kid’s going to do something like that,” said McDade, who works in finance in New York. “There was nothing that would indicate anything going on behind the scenes that would lead to this horrible mess.”
He recalled Adam Lanza as “a very bright kid.”
Olivia DeVivo, a student at the University of Connecticut, was in Adam Lanza’s 10th grade English class.
“He was very different and very shy and didn’t make an effort to interact with anybody,” she said.
DeVivo said Lanza always carried a briefcase and wore his shirts buttoned up to the top button. She said he seemed bright but never really participated in class.
“Now looking back, it’s kind of like `OK, he had all these signs,’ but you can’t say every shy person would do something like this.”
On Saturday, a police car was parked in the driveway of the Stamford, Conn., home of Lanza’s father, Peter Lanza. An officer stopped reporters who tried to approach the house.
Updated 12/ 17/2012:
NEWTOWN, Conn. — Newly public divorce paperwork shows that the Mother of Connecticut school shooter Adam Lanza (pictured) had the authority to make all decisions regarding his upbringing.
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The court papers were made public Monday. The divorce was finalized in September 2009, when Adam Lanza was 17.
Lanza killed his mother before going to Sandy Hook Elementary School in Newtown, Conn., on Friday morning and killing 20 children and six adults before taking his own life.
His parents married in June 1981 in Kingston, N.H. The file says their marriage broke down “irretrievably” and that there was no possibility of getting back together.
Watch a news report about Adam Lanza’s mother:
The divorce agreement gave Nancy Lanza $265,000 in alimony last year. It makes no mention of any mental health issues regarding Adam Lanza.