Tommy, the hitchhiker, says that the devil is a white man with black eyes and a mean hound dog.

The sheriff is a white man with a hound dog, who quite possible would have been at the crossroads at midnight looking for the three escapees.

Furthermore later on when the Pete is about to be hanged the sheriff has flames in his glasses lens's blocking out his eyes, indicating the fire of hell from below and when he walks into the shot it is quite scary, just the way Pete gasps when seeing him.

He says at the end the boys have come to their end and he's come to collect his due.