Factual error: The story takes place during spring of 1976 but Marty's parents drive a 1979 station wagon.
Factual error: When Marty is on the covered bridge, after running from the pastor, he hears a tractor running. He starts yelling for Mr. Zimmerman, who is driving the tractor, and Mr. Zimmerman stops the tractor and walks to the covered bridge. It would have been nearly impossible for Mr. Zimmerman to hear Marty yelling for him over the noise of the tractor.
Answer: Simple fight or flight response. His first thought is to fight whatever is stalking him. Once he discovers it's an actual werewolf he takes off.
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