Near the end of the film when the monster has crashed through the wall of the bar, the monster rips off his deer skull mask/helmet to show his true face. As soon as he tears the mask/helmet away, look carefully to the right of the screen. For a split second, you can see the black outline of a person standing beside it. This is revealed in the commentary. See more
Listen to me. A storm o'hell's coming down on this place any second. I don't know what they are, I don't know where they came from. All I do know is that these fuckers are fast, nasty, and hungry... and there's four of 'em. They got claws like Ginsu knives and more teeth than a chainsaw. They're comin'... right now. So we gotta lock this bar down. That means doors, windows, drains, and zippers, and we gotta do it now. You! Get a phone, call the cops, National Guard, townies, anybody who kicks ...