Mason is the main antagonist from the 2007 film, VACANCY. He was the manager to a dirty old motel where he makes cheap snuff films of people he rents the rooms to and sells them to a truck driver who doesn't know that the movies are real.
In the film, he rents a room to couple David and Amy Fox who were stranded when their car broke down.
When they get in somebody bangs on the door from the room, and David complains to the manager, but he just tells him not to worry.
Then, David finds one of the videos and puts it in the TV, and finds out that they're being made in the same room. He runs out to a pay phone and calls 911, but realizes that he was talking to Mason, and is then nearly run over.
He runs back to the room and find a trap door in the bath room to the manager's room where Amy calls the police, who is later killed. He kills David while Amy hides. He was shot dead the next day by Amy.