Some more ideas:
- Z could have asked Stine to look to the left shortly before shooting him from the passengers side.
- The first person arriving at the scene could have tried to pull Stine's body out of the cab to check his vitals or to try to revive him
(if you have ever touched a dead person, you know that the body 'feels' completely different - no muscle tension at all, feels like an object rather than a living body, feels and is quite heavy to move such a body, adrenaline boost etc., we are sort of programmed to 'safe' any other person, immediate urge of caring for this person, such a body feels very strange as it has no pulse etc.)
Overall I meanwhile do not think that Z had been sitting on the passenger's side as there are actually no indications for this except the open (or not open) door, which could after all have been opened to cut Stine's shirt.
What bothers me most is the blood on the floor. It really appears as if a head or other body part was lying there, blood dripping around but not onto the spot where the body part might have been. But later Stine was found quite away from that blood spot. That is really weird.
QT

