The line "I wouldn't turn him over" is Hemmingway's way of hinting at a gory shot which killed Francis Macomber. Aside from that quote, let's talk about the ending of the novel. It's a very odd one, to be sure. We know Macomber's wife wasn't a big fan of him, however when she shoots it says in the text that she's aiming at the buffalo--and Hemmingway has told us the truth about her thus far, right? The woman is bawling, and the man there with her, Wilson, kind of rubs Macomber's death in her face. He makes her understand that it was her fault even if she didn't mean for it to happen. In my opinion, it's not so important that Margot killed Macomber. It's more important that Macomber has escaped Margot's control and she now has nothing to control--which certainly is driving her insane.