This is an interesting sounding case where there has been a recent appeal for information. An interesting aspect is the apparent road block which made the victim stop:
Cold case: Troopers seek clues in killing of man at road-block trap:
MANHEIM - State Police say they need the public's help to solve the killing 42 years ago of a man who was ambushed by a gunman after someone blocked a rural road with tree branches and other debris.
Another report with more or less the same information as the above one:
State police looking for witnesses in cold case murder from 1977
Cold case: Troopers seek clues in killing of man at road-block trap:
MANHEIM - State Police say they need the public's help to solve the killing 42 years ago of a man who was ambushed by a gunman after someone blocked a rural road with tree branches and other debris.
Another report with more or less the same information as the above one:
State police looking for witnesses in cold case murder from 1977