By Josh Levs, CNN
(CNN) -- It was the end of the school day. The kids at Plaza Towers Elementary School were stuffing their backpacks, looking forward to going home, playing with friends, eating snacks.
But the tornado warnings changed that.
When the twister came barreling in Monday afternoon, terrified young students huddled together in the hallways, screaming as walls and roofs caved in. Chairs and backpacks swirled above them. The winds and blaring sounds enveloped them. Cars from the parking lot landed just inches away.
Teachers dove onto groups of kids to protect them from falling debris.
It was the biggest tornado they'd ever seen. Described as a lawn-mower blade spanning two miles, it shredded through their town.
"It was scary," student Julio Rodriguez told CNN. Teachers instructed the kids to crouch down, "and you covered your head with your hands," he demonstrated.
A first responder captured this photo at the scene of the devastated Plaza Elementary School in Moore, Oklahoma.
"I had to hold on to the wall to keep myself safe because I didn't want to fly away in the tornado," one little girl told KFOR.
The 17 mile-long twister stayed on the ground for 40 minutes.
By the time it was gone, so was the school in Moore, Oklahoma. In its place was a huge pile of rubble, trapping teachers and children.
And seven students were dead.
They were in a classroom, Moore Fire Department Chief Gary Bird told CNN Wednesday.
Lt. Gov. Todd Lamb told CNN Tuesday that the children were in a basement, where they drowned. But Bird said Wednesday that based on everything he's been told, "it had nothing to do with flooding."
In the tornado's wake, the school quickly became the epicenter of the tragedy in this shattered town, part of the metropolitan Oklahoma City area.