NEW YORK (Reuters) - Connecticut state police released a trove of documents and video on Friday tied to their investigation of the massacre at Sandy Hook Elementary School last year that killed 20 children and six adults.

The documents include footage of the school facade, including close-up images of bullet-shattered windows, and a video tour through the cheerfully decorated home the shooter, 20-year-old Adam Lanza, shared with his mother, Nancy Lanza.

The December 14, 2012, shooting rampage in Newtown marked one of the deadliest gun violence incidents in U.S. history. Lanza, who also shot and killed his mother before driving to Sandy Hook and forcing his way into the school he once attended, killed himself as police arrived on the scene.

Twenty first-graders, ages 6 and 7, and six staff members lost their lives.

The tragedy rocked the suburban town of 27,000 people and sparked a national debate about school violence and access to firearms.

Much of the material, which was posted on the website Cspsandyhookreport.ct.gov, has been redacted, and none of the images that speak to the carnage unleashed that day are visible.

"I hope that the release of this report, though painful, will allow those who have been affected by it to continue in their personal process of healing, and will provide helpful information that can be put to use to prevent such tragedies in the future," Commissioner Reuben Bradford said in a letter introducing the documents.

The release comes about a month after the state Division of Criminal Justice released a report on Newtown that concluded Lanza had acted alone, and that his motive may never be known.

The documents offer an eerie look into the life of the shooter, including an assortment of firearms and targets riddled with bullet marks.

One lengthy video shows the interior of Lanza's spacious Newtown home - off-white couches and chairs, brightly colored rugs and framed family photographs. Dirty dishes are in the kitchen sink and a telephone blinks with a new message.

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In a message sent out on Thursday, acting superintendent of Newtown public schools, John Reed, warned families of the release and the likelihood of media coverage surrounding them.

"Like you, I have not seen the materials, but I suspect for some persons, the contents will be an emotional trigger," he wrote, suggesting that parents might avail themselves of information from the National Trauma Stress Network.

(Reporting By Edith Honan; editing by Gunna Dickson)