Can anyone understand the ending of The Shooting?

The Monte Hellman (screenplay by Carole Eastman, of Five Easy Pieces) 1971 movie, The Shooting, is a strange and moody Western, all of it shot among the deserts, mountains, and bluffs of the far west, probably mean to be Nevada mining territory, and completely focused on 4 characters: Two miners, one of whom is a good trail guide and the other who is almost like a child in his naivete, a beautiful young woman who shows up out of nowhere and hires the men to guide her across the desert, and a malevolent hired gunman (played by Jack Nicholson), who turns up about halfway through. It's tightly scripted - almost like a domestic drama - and full of tension and mystery; we're pretty sure that the woman hired the men so that she could pursue and presumably kill a man (a friend of the miners) who may have harmed or killed her child - but this is all left vague and unresolved. It's entirely a film about mood, and it has many fearful moments, especially as supplies dwindle and they're faced with decisions about who to leave behind. The landscape is always terrifying and beautiful, and you can't help but think about how the actors, in their heavy Western outfits, must have suffered through much of the filming. All that said, the ambiguous ending completely eluded, and even after a re-watch I still have no idea who shot whom; ambiguity can be great, but filmmakers ought to at least throw a lifeline to their viewers. It's a film worth seeing, but having done so, I can see why it was a career backward-step for Nicholson and a dud with audiences.