US police have released thousands of documents related to their investigation into the killing of 26 people at a school in Connecticut.
Officials described as "painful" some of the details in the report
, which includes photos and transcripts.
It reveals new facts about the life of gunman Adam Lanza, 20, said to have suffered from mental health issues.
Lanza turned a gun on himself after opening fire at Sandy Hook Elementary School in Newtown in December 2012.
Before killing 20 children and six adults with a semi-automatic rifle, he shot dead his own mother at the family home. She had bought him the weapons used in the rampage.