I am trying to find a film, I think in black & white, could have been a western, mexico maybe, the scene I remember was in a church, mother holding a small child, a man playing russian roulette, small child grabs the gun, puts it to it's head pulls trigger and shoots themselves, most harrowing I have never been able to forget it, can someone help me find it?

El Topo (http://www.imdb.com/title/tt0067866/reference)