I like Occam's Razor. The more straightforward and likely answer is each one shot himself.They were reported to have both died from being shot, so must have shot themselves one way or another, or someone shot them and left them there in the scrub with two guns!
Besides, I think, regardless of whatever issues these two had, they did genuinely have a strong bond with each other. A toxic friendship but a strong one, nonetheless. For that reason, I think killing each other might have made them genuinely uncomfortable in a way that killing other people or themselves didn't.
MOO