After the second murder (Guy outside while main character is practicing screaming for her movie), The main character goes to the recording studio and a guy pops up in front of her in a connecting studio. The guy turns out to be the murderer. He goes over to the glass door and he breaks the glass. The camera goes to the girl then faces the door again. when it goes to the door, the glass is swinging back and forth because it is plastic or some other fake material.