Not sure what to make of this: The Road by Cormac McCarthy [musing time]

There's just one passage of McCarthy's The Road in the first person and I'm really not sure what to make of it! Really neat but it seems very out of place and also contains some breaks in continuity. I have an exam tomorrow in which I want to write about this, I'd love to see what other people think about it! Here is the passage:

The dog that he remembers followed us for two days. I tried to coax it to come but it would not. I made a noose of wire to catch it. There were three cartridges in the pistol. None to spare. She walked away down the road. The boy looked after her and then he looked at me and then he looked at the dog and he began to cry and to beg for the dog's life and I promised I would not hurt the dog. A trellis of a dog with the hide stretched over it. The next day it was gone. That is the dog he remembers. He doesn't remember any little boys.

One interpretation I've read is that the way in which this passage draws attention to itself is to signal the beginning of the man and woman from the end of the novel tracking the protagonist and the boy, and that it is this other man that is narrating the passage. This is a tempting explanation because of the present tense reflexive narration, that it is talking about the past in the present, but when? Because the protagonist of the novel dies. When does he narrate this moment? It's also tempting for me because at no point in the story time of the novel did the protagonist have three bullets in the gun. He had three before the story begins, but I believe his wife shoots herself with one. At the beginning, he has two bullets, but he uses one to shoot one of the "bad guys". So at this point in the novel, he should have one cartridge in the gun, not three.

On the other hand, the boy looks up at the narrator of the passage and begs for the dogs life. This passage occurs right after the boy sees the dog in the town as well as a little boy. Assuming we're talking about the same dog and the same little boy, it would have to be his father that says "I promised I would not hurt the dog."

Some people think the woman from the end of the book is referenced here, but I think it's just surprise to find the dog referred to as "she": "She walked away down the road." There's no reason this she can't be the dog.

Anyone have any thoughts? Please post even if you find this a year from now - my exam being past-tense has no baring on my curiosity over this enigma!