NEW YORK (AFP) - Newtown gunman Adam Lanza wore yellow ear plugs that muffled the screams of his victims and he shot himself in the mouth after committing one of America's worst school massacres.
Disturbing details about last year's mass shooting were revealed on Friday when US police released thousands of pages of documents, photographs and recordings from their investigation.
The troubled 20-year-old shot dead 20 first grade children and six adults at Sandy Hook Elementary School, using a rifle taken from his suburban mother's legally acquired home defense arsenal.
Lanza was dressed almost entirely in black, his clothes - a shirt, T-shirt, cargo pants, boxer shorts, socks, sneakers, belt and fingerless gloves - found spattered with blood and gunpowder after the murders.
"Two law enforcement officers arrived during the shooting, at which time the suspect ducked into a classroom and shot himself," according to an FBI incident report contained in the file.
Lanza shot himself in the mouth, shattering his brain and skull, according to the attached forensics report. The documents are the latest pieces of chilling evidence that expose some of the horror that Lanza's victims endured on Dec 14, 2012 in the small Connecticut town.
The massacre, just one in what was then a series of deadly shooting sprees across the country, inspired a short-lived and ultimately failed drive to tighten US gun ownership rules.
According to at least one witness interviewed by the FBI, Lanza and his mother Nancy owned at least four firearms, which were kept in a gun safe in the school shooter's bedroom closet.
Witness testimony, which has been redacted to remove names and other identifying details, also revealed little known details about Lanza, who suffered from Asperger's Syndrone.
The gunman was a vegan, interested in Japanese techno music and had been taking Chinese lessons. He also knew how to build a computer from scratch by assembling the spare parts.
His mother at one point took him out of school because he was sensitive to sound and light and photographs showed various windows taped over with white plastic and black bin liners. One door in the house was also shown taped shut.
Lanza carried out the murders the morning after his mother Nancy returned from a few days away, which she told one friend had been an "experiment" to allow him to stay home alone.
She told friends she was thinking about moving to the western state of Washington or to North Carolina to enrol her troubled son at a special school or get him a job to make him more self-sufficient.
The investigation was unable to find a motive other than to conclude that the killer was obsessed with mass murders and had "significant mental health issues".
Nancy Lanza and her son were said to have had a close relationship. She was not afraid of her son, but allegedly afraid for him.
Earlier this month, US authorities released recordings of emergency calls made by trapped and terrified people from within the school as the killer stalked the classrooms.
On the morning of December 14, Lanza shot dead his mother in the head as she lay in bed, then drove to the school. In collected evidence, a gun was seen lying on the carpeted floor of her bedroom.
Upon arriving at Sandy Hook Elementary, Lanza shot his way through the glass doors, photographs of the shattered scene showed.
He killed the school principal and a psychologist in the hallway, then gunned down two adults each in two first-grade classrooms, and shot 15 children dead in one classroom and five dead in the other.
Lanza took less than 11 minutes to carry out his crime.