Bnus kills people that he sees as a personal threat, which is not determined by their role, but how they play. Then, he targets you based on the importance of your role. Though he puts emphasis on those to categories, they aren't necessarily the first to go. Why? In chronological order the personal threats die first, and minor roles proceed to die. Finally, the major roles are taken out. The latter deaths often occur in tandem with the personal threats category, which can be expected for several reasons.
List: Threat--Civilian--charity--Major roles who aren't a threat.Charity are those he wants to allow a fair cushion of time to play, since they are new to the game. (and a bit of randomization)
It is hard to determine if the inconsistencies in the chronology of this list are due to the lack of viable evidence to convince others, or his own uncertainty. His uncertainty is counteracted by his dead-set playing style. He doesn't change his stance on a decision and professedly his known outlook on a situation. This allows his uncertainty to decay, which allows his decisions to be based on convincing appeal, such as in Unease's case.
In short, he targets people based on the evidence necessary to convince others, and how they will effect him.