There was evidence the Newtown school shooter had an interest in children that could be categorized as pedophilia, but there was no proof he ever acted on it, according to FBI documents released Tuesday.
The records were among more than 1,500 pages of documents released by the FBI in connection with its investigation of the December 2012 shooting at Sandy Hook Elementary School. Adam Lanza fatally shot 20 first-graders and six educators before killing himself as police arrived.
The records also say there was evidence Lanza began contemplating the attack as early as March 2011.
"The shooter did not 'snap,' but instead engaged in careful, methodical planning and preparation," the FBI's behavioral analysis unit wrote. "The shooter was fascinated with past shootings and researched them thoroughly. The shooter shared many similar characteristics and behaviors with other active shooters."
The behavioral analysis unit document did not say exactly what evidence there was that Lanza had a pedophilic interest in children. But another document says an unidentified woman told the FBI that Lanza said adult-child sexual relationships could be "possibly beneficial to both parties."
The woman, who said she had an "online relationship" with Lanza for more than two years before the school shooting, said Lanza did acknowledge that adult-child sexual relationships could be "unhealthy," and he did not express any personal sexual interest in children. She said Lanza believed he might be asexual.
She also told the FBI that Lanza compiled a spreadsheet that meticulously documented hundreds of mass murders and spree killings, but she didn't believe he would carry out a mass killing. She said Lanza also believed that mass murders were a symptom of a broken society and he may have believed he was "saving" children from the "harmful influences" of adults during the school shooting.
The documents include reports by FBI agents who interviewed people about Lanza. Large portions of many of the documents were redacted, including the names of the people who spoke to the agents.
The documents also offer a window into the early days of the investigation, as agents chased false leads and gathered evidence of Lanza's isolation.
A year after the massacre, state police released a final investigative document that concluded Lanza was obsessed with firearms, death and mass shootings, but that the motive may never be known.
That report also mentioned pedophilia. In it, state investigators said they had found a file on Lanza's computer that they described as "advocating pedophiles' rights and the liberation of children." They also said they found a screenplay describing a relationship between a 10-year-old boy and a 30-year-old man.
One person told an FBI agent that Lanza's mother, Nancy, had become concerned about him a month before the shooting because he had become a "shut in" who hadn't gone anywhere in three months. Adam Lanza shot his mother to death in their home before going to the school on Dec. 14, 2012.
The person also told the FBI agent that Lanza never completely accepted that he had Asperger's syndrome, a condition on the autism spectrum, and never took any medication he was prescribed.
"Nancy would take care of all of Adam's needs," the person said. "However, she never cleaned his room, nor was allowed in his room. Adam's room was his personal space that no one else was allowed into."
A report by the Connecticut child advocate in 2014 concluded that Lanza's autism spectrum disorder and other psychiatric problems did not cause or lead directly to the massacre. The report said Nancy Lanza rejected recommendations from Yale psychologists that her son be medicated and undergo rigorous treatment as a child for anxiety and other conditions. It also said Adam Lanza, his parents and educators contributed to his social isolation by not confronting his problems.
Another person told the FBI that Lanza essentially had become a "recluse" who played video games all day. The person said Lanza had no friends, was computer savvy and became very interested in firearms.
Lanza shot the children and educators with an AR-15-style rifle that was legally purchased by his mother, who took her son to shooting ranges, authorities have said.
A Newtown resident told the FBI that Nancy Lanza said Adam had once hacked into a government computer system and federal authorities — either FBI or CIA agents — showed up at their door.
Nancy Lanza told the person that she had to convince the agents that her son was just very intelligent and was challenging himself to see if he could hack into a government system. She said agents told her that if Adam was that smart, he could get a job with their agency someday.
Several Newtown residents told authorities they received death threats after the shooting during phone calls from someone identifying himself as Adam Lanza.