Said in an interview for the 30th anniversary edition of the movie that,
while playing the Graveyard Zombie, he was to smash the window of the
Pontiac LeMans
Judith O'Dea was trapped in at the cemetery with a rock.
Because it was a real car window, and not a breakable fake, he had to
hit it three times before it finally shattered. On the third time, the
rock flew out of his hand and bounced off the lens of the camera, which
was being operated by
George Romero. Hinzman was convinced that he had
accidentally killed Romero, who luckily was not hurt.