A shocking Friday report from Florida’s Sun-Sentinel details the myriad errors made by authorities and school officials during the February shooting at Marjory Stoneman Douglas High School that left 17 people dead. The newspaper’s investigation also provides previously unseen video footage of the moments before and after the slaughter. In one particularly chilling video, shooter Nikolas Cruz can be seen talking with a boy identified as freshman Chris McKenna in the first-floor stairwell of the school. When McKenna enters the stairwell, he sees Cruz preparing his gun. “You’d better get out of here,” Cruz said, according to the Sentinel. “Things are gonna start getting messy.” The report also revealed haunting images of Cruz stalking empty halls with his rifle, vulnerable students crowded in a hall after a fire alarm was triggered, and a school resource officer hiding for 48 minutes while students were murdered.