Thirty minutes before the end of the school day, gunfire started in Parkland, Florida

On Wednesday afternoon, 30 minutes before the scheduled end of the school day at Marjory Stoneman Douglas High School, Garrett Schreiber texted his mother and father that he loved them. All three knew it might be the last message he ever sent. A 19-year-old former student named Nikolas Cruz had broken into the school, set off a fire alarm to draw students out of their classrooms and opened fire with a semi-automatic rifle, according to after-the-fact accounts from local authorities. Seventeen people died, making Stoneman Douglas the site of the nation's deadliest high school shooting ever. Schreiber knew little of that as he and 60 of his classmates huddled shoulder-to-shoulder behind a desk. He heard the fire alarm; he saw school security guards running with their guns drawn.  Moments later, he heard the barrage of shots from Cruz's rifle and screams in the hallway outside.  Students who had stepped out to see what was happening streamed back into their classrooms -- through exits -- anywhere they believed would distance them from the gunfire. "We did hear a lot of yells and shouts, but we were told not to open the door just in case the shooter was there," he said. They waited like that, packed tight in a too-small space, for more than an hour. At home, a knock on the door brought the news to Schreiber's father, Matt.