It was parked towards the field, not directly at the gate.

Was he planning to abduct Betty or something? Shot Faraday dead, then planned and attempted to get in the Rambler and drive away with Betty as his prize, but Betty fled before he could pull away which forced him to exit the vehicle himself and open fire as she fled?

I know abduction was never Z’s M.O, but I’m just trying to figure out, if he ordered one or both out, why? Then again M.O for Zodiac seemed to change as often as his appearance seemed to

Why would he want to drive the Rambler away and leave his car behind (the one James Owen saw.) Unless you’re suggesting he was on foot and didn’t have his own car there?