The fire then swept down through the hallway ceiling's ventilation grates into the second floor corridor as it flashed through the cockloft above the classrooms. Glass transom windows above the doors of each classroom broke as the heat intensified, allowing superheated gasses and thick black smoke in the hallway to enter the classrooms. By the time the students and their teachers in the second floor classrooms realized the danger (and the occupants of several of the rooms, until that moment, did "not" realize the danger), their sole escape route into the hallway was impassable. The second floor of the north wing had become a perfect fire trap.