Trying to figure out what movie this is?

It's a horror movie. People go to the theatres and watch a horror movie. After they leave. If they ever said anything about someone getting hurt or dieing it started to happen. The killer dude or thing wore black and had sharp gl/razor things on his hand. not freddy crouger. Turned out that the movie in the theatres they watched had a hidden symbol/mesage that hypnotized a guy and he was the one doin the killings. I dont know who old it is. But I am trying to figure out what its called.