Story highlights "The weirdest person online" was how a woman who befriended Sandy Hook shooter describes him

Neighbor says federal agents visited Lanza home after he hacked an unidentified government computer

(CNN) A woman who befriended Sandy Hook shooter Adam Lanza online said he was "singularly focused and obsessed with mass murders and spree killings" and looked upon school shooters "with respect and understanding," according to heavily redacted FBI documents released Tuesday.

The unidentified woman began online contact with the 20-year-old about two years before his December 2012, rampage at the Newtown, Connecticut, school left 20 first-grade students and six adults dead.

"The weirdest person online" she said of Lanza, who "devoted almost all of his Internet activity to researching and discussing" mass killings he meticulously documented and viewed as "a symptom caused by a broken society," according to the roughly 1,500 investigative documents.

The woman told investigators that Lanza was "extremely intelligent" but depressed and cynical, with a negative view of the world.

Lanza's online posts included screen names that referred to German and Canadian school shooters Tim Kretschmer and Kimveer Gill, according to the woman.

Read More