In the first episode of the season, it appear that RJ was holding the box cutter (or whatever it was) in his left hand.  Smith and McAllister shot right handed, and Bertram appears right handed (holding cell phone).  Hard to tell about Stiles because he waves with his left but at other times appears right handed.  I have seen no clue regarding Haffner whether Haffner is right handed or left. I know it is a bit strange to offer a theory on a lack of eveidence, but  I think Haffner or perhaps Stiles.