I don't remember it too well but I do remember that the light was reflected a great deal by a large disco ball. Perhaps the light came in from one direction, and the faceted surface of the ball shot it in all directions.
No, the light only hits the mirror-ball as they walk out. Before it does that, it's coming in from all directions. Yes it should only be coming from the east.
Good ending though, better than Blade or Bram Stoker's Dracula.