Fade to Black(1980)

Eric is an obsessive movie fan works at a film distributor warehouse and screens old movies in his bedroom at night. When Eric runs into Marilyn O'Connor, a look-alike for Marilyn Monroe, he goes over the edge into a real psychosis and she becomes the target of his obsession. After believing that he has been stood up by Marilyn on what he expected to be their first date, Eric begins to disguise himself as his favorite movie characters and kill off his perceived enemies, working his way up to Marilyn.