THE 20-year-old suspected of America's worst mass school shooting at Sandy Hook Elementary in Conneticut was a "nerd" who enjoyed playing online computer games.
Adam Lanza, who was named unofficially as the gunman, is thought to have killed his mother Nancy Lanza at their family home where they lived before driving to the school to commit the massacre and taking his own life.
The 20-year-old may have suffered from a personality disorder but was considered to be academically gifted, while others have described him as a "nerd".
So far, the police have not spoken publicly of any possible motive behind the killings. They found no note or manifesto, and Lanza had no criminal history.
It is thought Lanza drove to Sandy Hook Elementary after killed his mother at the home they shared in a prosperous neighbourhood of Newtown. He took his mother's car and three of her guns, including a .223 calibre rifle.
Witnesses said the shooter didn't utter a word as he moved through the school firing weapons.
Lanza appears to have been a successful student who was intelligent if somewhat shy, according to former classmates.
At Newtown High School, he dressed more formally than other students, often wearing khaki pants, button-down shirts and at times, a pocket protector – a sheath designed to hold pens in a shirt pocket.
Tim Arnone, who first met Lanza at Sandy Hook Elementary, said they had both become members of the high school's audio-visual club, also known as a tech club, and spent free periods playing video games at the school's television station studio.
Students would also gather at a member's home, hook up their computers to a network and play games.
"It was definitely the nerdiest club in the school. We called it the tech club. We had our own little section in the room," Arnone, 20, told Reuters.
He said Lanza was "driven hard" to succeed academically by his parents, particularly his mother. "She pushed him really hard to be smarter and work harder in school," Arnone said.
Joshua Milas, who was another member of the club with Lanza and graduated from Newtown High School in 2009, said he had not seen him in years but remembered as an extremely clever student.
"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."
Gloria Milas, Joshua's mother, recalled a school meeting in 2008 organised 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."
Adam Lanza's name features among the Newtown High School's honour roll students. It is not clear if Lanza had a job nor if he had been in trouble with the police in the past.
Another former classmate, who declined to be identified, described Lanza as smart but without many friends.
He said he met Lanza when both boys joined the local Boy Scout troop.
At that time, he said Lanza was a big fan of Japanese culture, collecting Pokemon cards and playing the PlayStation video game Dynasty Warriors, a weapons-based animated fighting game released in the late 1990s.
"He was a very quiet kid," the friend said. "I remember being his only friend in elementary school. He was always a really nice kid, very polite."
Catherine Urso, who was attending a vigil Friday evening in Newtown, Connecticut, said her son had known 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'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 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 counselling, "Nancy wasn't one to deny reality," she told The Associated Press on Friday night.
Marsha Lanza said her husband saw Adam as recently as June and recalled nothing out of the ordinary about him.
Ryan was initially named as the gunman, but he took to the social networking site Facebook to insist he was not involved.
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 replied that his brother had been responsible and that he thought his brother was dead.