I saw this scary movie in the late 70s early 80s.  I want to say it was good vs evil.  I remember something about a large Catholic church and something about the devil.

The part I remember best is when a man rigs a way to kill himself.  In his office he sets up a shotgun by tying a rope to the trigger of the gun then the other end to the office door.  He placed the gun so it aimed right where his head would be while sitting in the chair.  He sits in the chair and when someone opens the door the gun goes off and blows his brains all over the wall.

This movie has driven me nuts for years, no-one remembers it and I want to see it again.