The Connecticut state police will release its final report on the Sandy Hook Elementary School shooting on Friday.

NEW YORK -- Connecticut state police plan Friday to release a trove of information from the investigation into the Sandy Hook Elementary School massacre last December, perhaps shedding more light on the gunman's mental condition and his reason for targeting the school.

The unsealing of the report comes more than a year after Adam Lanza killed 20 first-graders and six adults in Newtown, Conn., and will mark the final release of information from the police probe into Lanza's rampage.

In a statement, police said it "runs several thousand pages and has been redacted according to law."

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In addition to text, it also will include photos and 911 calls received by state police on Dec. 14, 2012, when Lanza, 20, shot his way into the school at about 9:30 a.m. Lanza already had shot to death his mother, Nancy Lanza, in their Newtown home, and he committed suicide in the school.

A summary of the police report, released last month, revealed for the first time the depth of Lanza's mental illness and isolation. That summary described his apparent obsession with mass murders, his social awkwardness, and his mother's concern about his downward spiral.

Among other things, it said Lanza kept a spreadsheet of mass murders, hated to be touched, and covered his bedroom windows with black trash bags. He refused to speak with his mother except via email even though they lived together, the report said. It added that despite Nancy Lanza's worries about her son, she kept several legally purchased guns in her home, along with ammunition, and had given Adam a check to buy himself a gun for Christmas.

Adam Lanza used his mother's guns to kill her, to attack the school a few miles from their home, and to kill himself.

The report summary also concluded that Adam Lanza had worked alone in planning and carrying out the massacre and that no charges against anyone else would be filed.

Officials in Connecticut have been slow to release information from the shootings, and the state's attorney for the Danbury region, Stephen Sedensky III, went to court to try to keep sealed the recordings of 911 calls made to police the day of the massacre.

A judge sided with media outlets and with the state's Freedom Of Information Commission, which argued that the 911 calls were public record under state law and should be unsealed. Police have not said why it took more than a year to produce the full investigative report, but they had said from the start of the probe that hundreds of people needed to be interviewed, and that law enforcement authorities needed time to try to access information from computers found in the Lanza home.

Some relatives of Sandy Hook victims, and local officials, argued that releasing the information would force them to relive the tragedy and would not provide the public with any useful material.