Video details the moments before Florida school shooting

A newly released interview with a security monitor at Marjory Stoneman Douglas High School describes what happened immediately before the shooting that killed 17 people.

The video released by Broward County prosecutors Tuesday was recorded shortly after the Feb. 14 shooting. Andrew Medina told detectives he saw Nikolas Cruz get out of an Uber with a large bag and make "a beeline" toward the freshman building.

Medina said he recognized Cruz as a troubled former student and immediately radioed another unarmed security monitor to "keep your eyes open." That monitor hid in a janitor's closet in the building when shots rang out. Medina said he immediately recognized it as gunfire and drove his golf cart to pick up Deputy Scot Peterson.

Some parents say Medina should have called in a "code red," but he said he didn't know Cruz had guns.