There is the possibility that the report was actually filed by one of the crew members involved, claiming to be a passenger. Just to get the story out and to assure that something is done about it. Airlines seem to treat things different when it is more public than when it is handled in-house.
The reason I say this is because it does seem a bit odd to be able to hear yelling from the passenger cabin of an AT72, through two doors and some bags. Again, not saying it is impossible, just a little far-fetched.
Then again, maybe they did hear it, especially if the FA opened the door to check it out.