spoilers:end of spoilers
The mood is a bit of a strange one. It's hard to project the tells of human body language onto the police footsoldiers, with their non-human physiology they simply don't move or react like conventional humans. The strongest vibe that Krys can get from the shamblers is that they are "driven" and perhaps a little dazed. When they are hit with arrows, they don't react quickly, almost like they don't feel that much pain but are still driven to retreat.
Their leader, as far as Krys can tell, seems to be forthright in his declarations. Mushed and slurring his voice may be but there seems to be a core of belief within it. This being seems to believe in justice and that he represents an authority that has legal jurisdiction here. Krys notes that there's not much discussion of what could happen to the offenders /after/ the surrender and they have enough knowledge of the concept of punitive justice to have ideas about what that might mean.
The defenders in the building under siege are a bit too distant to get much of a read on them as they are moving from window to window, dodging shots and firing back. Krys can just about catch a glimpse of some clearly yelling others. Perhaps panicked? They are, after all, trapped and being fired upon by inhuman, smelly monsters.