Sedensky delved into the background of Lanza's life in a quest to find a motive for the Sandy Hook massacre. Sedensky says his report does not do that.
"Unfortunately, that question may never be answered conclusively. The evidence clearly shows that the shooter planned his actions, including the taking of his own life, but there is no clear indication why he did so, or why he targeted Sandy Hook Elementary School," Sedensky wrote in the report.
The report, however, is telling as much for what it did not find as what it did reveal.
Lanza did not appear to have been physically bullied nor did he harbor any specific grievance for Sandy Hook Elementary School, which he attended until the first half of his fifth-grade year. Lanza and his classmates were the first Newtown fifth-graders to attend the intermediate school, moving from Sandy Hook Elementary School to Reed in mid-year in 2003. None of his teachers reported Lanza's being physically bullied at Sandy Hook.
In fact, Sedensky said Lanza "loved the school and liked to go there."
Sedensky did find that Lanza "had evaluations of various types" from the late 1990s and into the 2000s though Sedensky does not specify who conducted those exams.
Sedensky goes back to preschool when Lanza had problems with his speech and was being "followed medically for seizure activities," the report said. He had temper tantrums, reported smelling things that were not there, washed his hands excessively and developed "eating idiosyncrasies," the report said. He refused to touch door handles and "often went through a box of tissues a day to avoid the contact."
By 2005, Sedensky said, Lanza was diagnosed with Asperger's syndrome after showing signs of "extreme anxiety" and social problems. Sedensky does not cite the source of the diagnosis, saying only that Nancy Lanza "consistently described" Lanza as having the disorder, telling friends and family that her son was unable to make eye contact with people, was sensitive to light and displayed repetitive behaviors.
In 2006, Nancy reported marked changes to her son's behavior. She said he no longer rode his bike, climbed trees or played the saxophone or sports.
By the ninth and 10th grades, Lanza had taken to shutting himself inside his bedroom, spending hours on end playing such video games as "Call of Duty," "Grand Theft Auto," and "Combat Arms."
But Lanza was on the radar at Newtown High School. He was designated a special education student at the school, and was a member of the tech club, where acquaintances and advisers recalled him as quiet and smart. He wore the same clothing repeatedly, "and might not speak to you, even if you were talking to him,'' Sedensky wrote. But no one recalled his being bullied or speaking about overt violence, the prosecutor said.
Sedensky said it is unclear how Lanza's mental health issues might be tied to the massacre.
"Those mental health professionals who saw him did not see anything that would have predicted his future behavior," Sedensky wrote.
At home, in the spacious house he shared in Sandy Hook with his mother Nancy, his peculiar needs were met, including a special diet, right down to certain dishware and food textures, and a tolerance for Lanza's hatred of Christmas, holidays, birthdays and pets. The mother agreed not to have a Christmas tree and got rid of the family cat, Sedensky wrote.
She also indulged her son's obsession with firearms, intentionally or not. Sedensky said firearms and target shooting were a "pastime" of the Lanza family.
"Over the years the shooter enjoyed target shooting and would go to a range with his brother and mother. The mother had grown up with firearms and had a pistol permit," Sedensky wrote.
"Both the mother and the shooter took National Rifle Association (NRA) safety courses. The mother thought it was good to learn responsibility for guns. Both would shoot pistols and rifles at a local range and the shooter was described as quiet and polite," the prosecutor said.
Nancy Lanza had planned to give her son a pistol for Christmas last year.
Having cut off his older brother, Ryan, and father, Peter, in 2010, Lanza depended heavily on his mother, though witnesses told Sedensky that their relationship was strained and they communicated only by email during the last year of their lives.
Lanza was loathe to leave the house, but Lanza seemed to support his mother's idea of moving to Washington or North Carolina. The mother had planned to buy a recreational vehicle so that mother and son could travel, Sedensky wrote.
Nancy Lanza, who traveled frequently, was away in New Hampshire during the week before the murders, returning home on the eve of the rampage.