Continuity mistake: During the final chase scene where Melanie Kinnamin is running through the woods the pink sweater which is over her shoulders disappears and reappears at random, until she finally loses it by the tree where her co-worker is found murdered.
Plot hole: At the end when Tommy is in the hospital, he gets out of bed and goes over to the drawer where his belongings are. He opens the drawer and there's the mask the killer was wearing. How did it get there? The police would take that as evidence. There is no way that police would let Tommy keep this mask for a souvenir.
Revealing mistake: When Reggie hits Roy with the tractor, the wound on his chest only appears after he has hit the ground.
Continuity mistake: Just before Junior is killed, the level of the stew Ethel is making changes from shot to shot.
Continuity mistake: After Reggie's grandfather flies through the window, his head changes positions between shots.
Plot hole: When the couple go into the woods to have sex, after they finish, the guy goes to a pond to clean up, which is not very far from where he left his girlfriend. A couple minutes later, "Jason" is about to kill her, and she screams very loudly. Despite this he doesn't hear her.