Family and friends remember Adam Lanza as many things -- intelligent, nerdy, goth, remote, thin.
Now the world will always remember him as a mass murderer. The 20-year-old man is believed to have killed his mother, gunned down more than two dozen people, 20 of them children, at a Connecticut grade school and committed suicide.
He might have suffered from a personality disorder, law enforcement officials said.
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.
Adam Lanza attended Newtown High School, and news clippings from recent years show him on the honor roll. Joshua Milas, a classmate who was in the technology club with Lanza, said that he 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," said Milas, who graduated in 2009. "He was probably one of the smartest kids I know. He was probably a genius."
The tech club 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, Joshua's mother, hosted one of the parties once.
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."
Catherine Urso, who attended 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," referring to a style of dress noted for a heavily black wardrobe.
Authorities say Adam 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.
Investigators were trying to learn as much as possible about Lanza and questioned his brother, who is not believed to have any involvement in the rampage.
Ryan Lanza, 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 Adam Lanza might have had.
Ryan Lanza had been cooperative and was not under arrest or in custody, but investigators were still searching his computers and phone records. The brother told law enforcement he had not been in touch with Adam since about 2010.
Adam 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.
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.
Lanza's aunt Marsha Lanza, of Crystal Lake, Ill., said her nephew was raised by kind, nurturing parents who would not have hesitated to seek mental help for him if he needed it.
If her son had needed counseling, "Nancy wasn't one to deny reality," she said Friday. Marsha Lanza said her husband had seen Adam as recently as June and recalled nothing out of the ordinary.
Lanza said she was close with Nancy Lanza and had sent her a Facebook message Friday morning asking how she was doing. Nancy Lanza never responded.
Nancy Lanza's mother 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 Adam Lanza attended Sandy Hook school several years ago but appeared to have no recent connection to the place.
At least one parent said Adam 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.
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.