Blow Out (1981)

This stylish Brian DePalma thriller plays off the theme of the unsuspecting witness who discovers a crime and is thereby put in grave danger, but with a novel twist. Jack is a sound recordist who works on grade-B horror movies. Late one evening, he is recording sounds for use in his movies when he hears something unexpected through his sound equipment and records it. Curiosity gets the better of him when the media become involved, and he begins to unravel the pieces of a nefarious conspiracy. As he struggles to survive against his shadowy enemies and expose the truth, he doesn't know whom he can trust.