What is this Depressing Movie?
 

I need your help mofos, for years I have tried and tried to find this movie:

It's from the 70's-early 80's I believe, it has this entirely somber tone throughout, and the scene that sticks out in my head the most is an elaborate suicide where this guy in his 40's-50's kills himself in his office by setting up an device where whoever opens the door triggers a gun to shoot himself in the face.

It has been so long ago that I am unsure what country the movie was made in, and I cannot remember if the character had a momentary regret over his plan, and by then it was too late. However, the depressing nature of the scene was unmistakable.

Please help.

I think that is The Omen III: The Final Conflict (1981)

Can't post links yet, but it is on Youtube, when you search for Barbaras Baby Omen III 1981 and then skip to 10:44

That's it! A while ago I tried watching The Omen I and I believe 2, but I guess I should have kept going. Thank you Bubblezzz!