Crime scene ... a smashed hard drive belonging to the killer, Adam Lanza was found at his house. Photo: Reuters
NEWTOWN, Connecticut: Police have been unable to recover data from gunman Adam Lanza's computer after the 20-year-old deliberately sabotaged the machine's hard drive, investigators have said.
Forensic experts revealed the software had been smashed so extensively that attempts to retrieve potentially crucial evidence such as emails had failed.
A joint effort to piece together the remains of the hard drive, reported to have been damaged with a screwdriver or hammer, was undertaken by Connecticut State police and the FBI.
Authorities had hoped its data would shed some light on Lanza's killing spree. Detectives have so far been unable to provide any definitive link between the young man and the school he attacked.
''It looked like he took steps to damage it - he smashed it,'' an official connected to the investigation told The New York Times.
Federal investigators have interviewed at length both Lanza's father Peter, a tax specialist, and his elder brother Ryan, 24, But despite hours of questioning it is understood the pair were unable to explain why Lanza acted so violently.
Lieutenant Paul Vance, a spokesman for state police, said investigators were continuing to ''examine everything and anything'' relevant to the shooting, including mobile phones and computer game consoles.
Officials said they were also aware that Lanza had been a keen computer gamer, and enjoyed some of the particularly violent varieties of war games.
FBI investigator Robert Paquette said: ''Many of these games are very violent. I can't help but believe these can affect someone unbalanced.''
No letters or notes from Lanza have been found offering a motive for his actions.
Police are also likely to concentrate their efforts on statements provided by vice-principal Natalie Hammond, 40, who is recovering in hospital after being injured in the shooting.
The teacher, along with a second survivor who is understood to be an employee at the school, will be vital in helping piece together an explanation for the tragedy.
A spokeswoman for the Office of the Chief Medical Examiner in Farmington, Connecticut, confirmed that no family member had yet come forward to claim the bodies of Lanza or his mother. All other victims of the shooting had been handed over to loved ones.