I really like it, the ambiguity of the story, the openess of the ending. The only thing I would have to say is that the beginning "Have an apple" could have been a stand alone sentence just like in the end, to kind of tie it all together, instead of part of a larger sentence. Nevertheless, a very satisfying read, thank you.
The story, had a good flow but felt a little choppy. Maybe you can develop the character of Billy and Charlie a little bit more, tie them in with a bit more emotion. There are some sentences that could be compacted so the story flows a bit smoother, but overall good story just needs more emiotional tug.