US school shooting: Profile of suspected gunman Adam Lanza

Former classmates of Adam Lanza, 20, the man identified by US media as the gunman in the Sandy Hook School killings, do not remember much about him.

They talk of a boy who dressed smartly and worked hard, but who barely said a word during his time at school.

Police are investigating whether he had a personality disorder.

Lanza was "obviously not well", a relative told ABC News.

He appears to have shunned the limelight. US media report that there was no photograph of him in his high school yearbook of 2010. "Camera shy" was the comment by his entry.

He apparently had no Facebook page and his electronic footprint was minimal.

'Shy and nervous'

Adam Lanza lived with his mother in a well-to-do neighbourhood of Newtown, Connecticut. The house is about five miles (8km) from Sandy Hook School, which some reports said he had attended in his youth.

He went on to Newtown High School, but made few friends. ABC News has reported his mother pulled him out of the school and taught him at home because she was unhappy with the school district's plan for his education.

Intelligent but shy and nervous were the most common memories of those who learnt beside him.

A former classmate, Olivia DeVivo, told the New York Times: "I never saw him with anyone. I can't even think of one person that was associated with him."

Another former classmate, Joshua Milas, described him as "probably one of the smartest kids I know. He was probably a genius".

A former school bus driver in the town, Marsha Moskowitz, said she remembered the Lanza boys.

"You know the trouble kids, and you figure, 'Pfft, that one's going to be trouble.' But I never would have thought that about them," she told the Hartford Courant newspaper.

His aunt, Marsha Lanza, told the Associated Press that he had been raised by kind, nurturing parents, who would not have hesitated to seek counselling for their son if he needed it.

The parents divorced in 2009, having separated at least three years earlier. His father, Peter Lanza, moved to Stamford, Connecticut, and remarried three years later.

His mother, Nancy, remained in the family home, where it is thought she was killed by her son. She had continued to work as a teacher.

Adam Lanza's elder brother, 24-year-old Ryan, had moved to Hoboken, New Jersey, after graduating from Quinnipiac University in Connecticut. He works for the accountants Ernst & Young

His friends described him as smart but shy.

Ryan Lanza has been helping police with their investigation and US media is reporting that he told them he had had no contact with his brother since 2010.

The two boys were reportedly deeply affected by their parents' separation and divorce. Neighbours say they were left depressed, but their mother had continued to work to protect them.