usually to kill in a room is easy, jut use water hose. but when fire gets into the wall, you have to knock down any wall or ceiling that might be burning inside, this is a very physically demanding job.
And after all fire is extinguished, the FFs have to remove charred wood from walls and take to outside. This techincal term is call the overhaul, again very back breaking hard job.
this case the fire department didn't do a good job at overhauling.