Identify the film

Im wondering if anyone can help me to identify the western i watched as a youngster with my pappy…the only part if the film i remember is a scene where a couple of cowboys are on a hill overlooking a ravine and them spying on this other cowboy and his wife as they go to the toilet together in the bushes and how they go to the same spot everyday to do their ablutions. Then when they are vulnerable with their pants down they shoot them both. I can picture the scene vividly but i dont know anymore it was probably about 40 years ago i sat with him and watched it