FBI docs shed disturbing new light on Sandy Hook killer Adam Lanza

NEWTOWN, Conn. — Newly released FBI documents are shedding more light on the investigation surrounding the 2012 massacre at Sandy Hook Elementary School in Newtown, Connecticut.

Adam Lanza shot his way into the school on the morning of Dec. 14, 2012, and was able to murder 20 first grade students and six teachers.

He later killed himself inside a classroom.

The FBI released nearly 1,500 pages of information that detailed the investigation including witnesses and evidence collected from Lanza’s home that he shared with his mother.

She was shot and killed by Lanza while she was asleep in her bed the morning of the massacre.

WATCH: FBI Releases Documents on Sandy Hook Killer Adam Lanza

Information in the report shows Lanza started plotting the shootings as early as March 2011 and hated Sandy Hook because he said his mother worked at the school and felt she loved the students more than she loved him.

Lanza’s mother was a volunteer at the school.

The report also details how Lanza researched and kept notes on other mass shootings and said he was “focused and obsessed with mass murders.”

Investigators also said Lanza may have had an interest in pedophilia, but there was no proof that he acted on any of those urges.

The report also said the FBI found a file on Lanza’s computer “advocating pedophiles” rights and liberation of children, along with a screenplay describing a relationship between a 10-year-old boy and a 30-year-old man.

The FBI documents also said Lanza was into computers and even hacked into a government computer system.

The report released by the FBI has been heavily redacted.

An unidentified woman in the report told the FBI she had an online relationship with Lanza years before the shooting.

She met him on a website devoted to the 1999 massacre at Columbine High School in Littleton, Colorado. She recalled Lanza saying he may be asexual, but she also described him as depressed and cynical with a very negative view of life.

The documents showed Lanza was a recluse and just three months before the mass shooting the 20-year-old’s weight dropped to 85 pounds.

And according to the FBI’s behavioral analysis, Lanza didn’t “snap” but instead engaged in careful, methodical planning and preparation.