Some attendees who bolted after the gunshot at Utah Valley University rushed into two classrooms full of students, where the periodic table adorned the wall and formulas were written in blue on the whiteboard.

They pulled tables from the center of the room to barricade the door, stacking them atop each other.

Others were turned on their side in a corner in a last ditch defense. Desperate, someone grabbed an electric pencil sharpener and wrapped the chord tightly around the door handle, then tied the sharpener to a chair leg.

Thursday morning, the classrooms were quiet and in disarray. Backpacks and notebooks were left on the desks, some scribbled with notes on electromotive force in green pen and pink highlighter.

AP Video shot by Jesse Bedayn