One person told the FBI that Lanza's mother, Nancy, had expressed concern for her son a month before the shooting. Nancy said that he had become a "shut-in" who hadn't gone anywhere in three months, according to Daily Mail. In his last month, Lanza had dropped to just 85 pounds.
"Nancy would take care of all of Adam's needs," the person told the FBI. "However, she never cleaned his room, nor was allowed in his room. Adam's room was his personal space that no one was allowed into."
Another person also told the FBI that Lanza had become a "recluse" who played video games all day. It was reported that he had no friends, was computer savvy and became extremely interested in guns.
A woman that interacted with Lanza said that he was "the weirdest person online." She says that his screen names were created in honor of other infamous school shooters like German gunman Tim Kretschmer and Canadian killer Kimveer Gill.
"He was singularly focused and obsessed with mass murders...Lanza devoted almost all his internet activity to researching and discussing mass murders and spree killings," an FBI summary of the December 2012 interview reads.
The person interviewed by the FBI agent also said that Lanza never accepted that he had Asperger's syndrome. It was also reported that he never took any of the medication he was prescribed for the condition.
The report also claimed that Nancy rejected recommendations from Yale psychologists that said her son should undergo rigorous treatment as a child for anxiety and other conditions.
Four years before the shooting, one man told the FBI that Lanza had threatened to kill his mother and attack Sandy Hook.
"Lanza hated his mother and Sandy Hook because his mother had worked there," a summary of the interview reads. "Lanza apparently felt his mother loved the students more than she loved him."
Just before going to the elementary school on December 14, 2012, Lanza shot his mother to death in their home. Lanza used firearms that were purchased by his mother in the shooting.