The Beast from 20,000 Fathoms - Back from the Belly of the Beast
When the "Rhedosaurus" comes ashore in New York, and panic ensues, a lone cop fires at it with his pistol. In a memorable scene, he tries to reload his gun and the monster has him for lunch. Yet a moment later, you can see the very same cop again as part of a group of patrolmen who fire on the dinosaur!