Alright, let me clear out some of the rumors here:
The king had multiple advisers and one of them stabbed him in the back (poisoned) for a large amount of gold paid by... nobody really knows.
The guilty adviser was killed whilst trying to escape by three arrows in his back.
The local guard is trying to trace the origin of the gold back, but is having trouble with it.
The new emperors uncle was/is also an adviser and rumors are going around that he might have paid the other adviser to murder the king, but those are just... ya' know... Rumors!