It may look that way, but more knowledgeable people than me have looked at this and firmly believe that Finicun was shot and that is his flinch reaction. I believe his daughter. He was unarmed. No one in the vehicle was shooting. This was an ambush. Was Finicum pissed off? Clearly. Did more than one person shoot him? Yes. Did they leave him dying in the snow? Absolutely.
He's messing with some wires.
Also, he's got a right-hand holstered handgun.