I just realized the above theory about the wolves excludes me - and there is nothing more wolfish than excluding oneself with a theory.
Although I am neither inexperienced, nor under pressure, as a wolf I might have killed
Brinn (in certain moods) just to create the impression the wolves were either of those things.
Other than me, I might suspect
Nogrod...
Fea... and
Boro... of such shenanigans.
Brinn's death also proves that
Boro defended, and
Nogrod attacked, an innocent. Not sure where to go with that...
EDIT: X'd with Mith and a huuuuuuge post from Nog