When Nikolas Cruz started shooting last week at Marjory Stoneman Douglas High, an armed deputy stationed at the Florida school rushed to the building.
But instead of going inside, the officer waited outside for four minutes as the gunman killed students and faculty inside, authorities said.
School resource officer Scot Peterson never went in, despite taking a position on the west side of Building 12, where most of the carnage happened, Broward County Sheriff Scott Israel said Thursday.
Asked what Peterson should have done when gunfire broke out at the Parkland school on February 14, Israel said the resource officer should have gone into the building.
"Addressed the killer. Killed the killer," the sheriff said.
Israel suspended Peterson without pay pending an investigation. Peterson chose to resign, he said.