Here's one report of a scream.

Here's a scream...
"
Room 204, Professor Librescu’s class, seems to have been the gunman’s last stop on the second floor. The teacher and his dozen students had heard too much, though they had not seen anything yet. They had heard a girl’s piercing scream in the hallway. They had heard the pops and more pops. By the time the gunman reached the room, many of the students were on the window ledge. T" [+]

Earlier, I couldn't understand why I wasn't seeing reports including screams-- but maybe under duress-- like this-- people don't scream a lot.