A massive report from the Connecticut State Police released online Friday offers new details about the Dec. 14, 2012 shooting that killed 20 first-graders and six educators at Sandy Hook elementary school in Newtown, Conn.

According to NBC News, the 7,000-plus page report includes investigative files, 911 call transcripts, crime scene reports and thousands of photos. The report also includes more than four hours of video taken by investigators inside the school. The video has been heavily edited and doesn’t show any bodies of victims.

The report, quoting an anonymous witness, says that Lanza may have targeted the school because his mother Nancy had once worked there. Lanza killed his mother before heading to the school, where he ultimately took his own life.

A preliminary report issued in November said there was “no conclusive evidence” about Lanza’s motive.

Tom Winter, Hannah Rappleye, Monica Alba and Kristen Dahlgren of NBC News contributed to this report.



