classrooms-- MSM unclear about number of classrooms but it's apparently 4? How?

"Now we are hearing that victims were found in four classrooms. While he is in one classroom blasting away, what are the other students doing? Just sitting there waiting? They would have either fled or barricaded the doors, like students in other classes did. One witness reported conversation in the hallway. I am thinking at least two shooters, with three or four possible." [+]