Approximately 1,500 heavily-redacted FBI documents related to Sandy Hook shooter Adam Lanza were made public this week. The documents reveal what the FBI’s behavioral analysis unit classified as “careful, methodical planning and preparation.” The bureau lists that behavior as part of the reason further action wasn’t taken to prevent Lanza from killing 20 first-grade students and six adults during a 2012 rampage at the Newtown, Connecticut school.

One entry details a man whose name was redacted specifically alerting authorities about a conversation in which Lanza said he had an assault rifle and planned to kill his mother as well as children at Sandy Hook. According to the document, the man reported the conversation to the Newtown Police Department in 2008, only to be told “Lanza’s mother owned the guns and that there was nothing N.P.D. could do about it.”

It’s unclear if the tips could’ve led to any legal action under Connecticut law, as Nancy Lanza legally purchased the weapons her son eventually used to kill her, the 26 victims at Sandy Hook, and eventually himself.

Other tidbits from the trove of redacted documents include testimony from a woman who met Lanza online roughly two-and-a-half years before he committed his killings.

“Lanza was working on a list, or spreadsheet, meticulously documenting the details of hundreds of spree killings and mass murders,” FBI agents wrote of their interview with the unidentified woman. She also says Lanza told her “adult/child sexual relationships as possibly beneficial to both,” which matches up with reports of his interest in pedophilia.

The full FBI report, detailing everything from Lanza’s relationship with his mother to his habit of avoiding daylight is available at the official FBI website.