Police released thousands of pages from their investigation into last year’s massacre in Newtown, Connecticut, providing the most detailed and disturbing picture yet of the rampage.

It’s a year to the day since Kaitlin Roig barricaded herself and 15 first-graders in a bathroom at Sandy Hook Elementary School, hiding from a gunman who would go on to kill 26 in an 11-minute rampage.

A worker who turned on the intercom, alerting others something was wrong.