Continuity mistake: The sound that startles Lana was breaking of plates. But when she investigates, she finds the cat sniffing fallen pots. (00:34:40 - 00:35:50)
Continuity mistake: When Demon is in the outhouse and the wall is speared the first time you can see the pike coming in above the toilet paper roll. When it cuts the pike is almost below the roll. (00:53:15)
Continuity mistake: When Violet is dancing in her room, Jason starts to walk up to her and we see the knife has dried blood on it. Then he picks her up, stabs her takes the knife out and now the knife is clean. (01:04:55)
Continuity mistake: Lana smears lipstick on her upper right lip, but when she turns at the cat's noise, it is pressed and perfect-looking. (00:34:40)
Continuity mistake: When Jake gets a cleaver smacked in his face, you see him get slashed across his face. When Robin goes to bed and she sees his dead body, you can see the slash on his face is in the opposite direction. (01:01:15 - 01:03:30)
Answer: He simply just snapped. He definitely looked angry before Joey even started talking to him, and said how he hated being there...and he already had an axe in his hands...he just lost it, and took out his anger and frustration on Joey.