Alright, so we only see this working one way. In our minds, the speaker has to be a bow-legged skinny old guy, with a voice like gravel on a tin roof. He’d need a big white mustache and a cigar chomped between his teeth. He’d have a twangy southern accent and maybe a missing finger on his right hand that he won’t talk about. Some poems could have all kinds of speakers, but for one like this, a ballad of life and death on the frontier, well it just wouldn’t work with anyone but this guy. Try to imagine someone else telling this story: an English aristocrat, a French ballet teacher, a computer programmer? We just don't see it. There has to be some trail dirt left on our speaker’s clothes, and a voice and a face that lets us know he’s lived hard, seen a lot, and survived to tell the tale.
But maybe that's just us. The poem doesn't give us many clues about the speaker. How do you picture him?