The story as it comes out is that, just after you left, they sent word to Castle Refuge that a series of raids had occurred again. These has happened before, but some application of firepower by the Coffin Nails had ended the threat. The beastmen were driven off.
Now they're back, attacking the outer homes and raiding for food or supplies. So far, no one has been harmed that they know of, but they're pushing further into Cartouche.
While they are surprised at how fast you got here (which is why the bunk house wasn't quite ready), they assumed you had been sent to deal with it.