Goofs

At the very end of the film, Christopher walks back into the lake and submerges. Once submerged, the scene cuts to a much more broad picture of the lake in which the credits start to roll. If you look very closely at the right side of the picture, you can see a person walking along a path that is on the right edge of the lake. It is clearly Christopher because he has the same blue shirt and maroon pants on.

Obvious discontinuity between the shots when the killer pours a powder in the water. It is supposed to look like one continuous shot, but it's not because the cut is obvious.

When the director asks what the hell is Roger doing, he is clearly not in the position he was in previous shot.

When Terry arrives to the reunion, John was not holding a hand on the car in the previous shot, but in this shot he is.

Janitor moving his hand slightly when the killer put photos next to his hand while being dead.

When Kirsten is screaming at the gate, she could obviously see that the person approaching her is weird and is carrying a scythe.

John can be seen breathing after he's been shot dead through the head.

Clearly alive man pretending to be dead when Janitor is found. He's also moving when everybody comes to examine him.

Janitor clearly moving his eyes after the scene with a joke in a locker room while being dead.

Ritchie supposedly slams Terry's hand by the car's door, but Terry obviously pulled the hand back before, but still acts as if he was hurt.

When first victim is found, the woman screams, but the pair coming down the upper floor acts as if they didn't hear her even though she screamed so loud probably everyone in the building could hear her.

Even though Jane knows a lot about guns she runs from the killer instead of laying low and increasing her chances of survival.

Microphone is not stuck in Terry's mouth, yet Roger says it is.

When Cindy finds out the door is locked, she obviously went by the doors on the floor below which clearly lead outside without trying them first because she reacts puzzled when she can't open the door meaning it's her first try to get outside.

After they discover there are bars on the windows, Kirsten is outside screaming at the gate without an explanation how she got out. If they can go out, bars don't matter.