A. Arsat leaves him behind to be captured and killed.
In the narration, Arsat says he heard his brother call his name, but he kept pushing the canoe. He says he "never turned back". This shows that he left his brother behind. Then Arsat indicates that his brother's voice changed to more of "a great shriek, as when life is going out together with the voice". From this we can infer that his brother has died. There is no indication that his brother had a different canoe, suffered from a fever, or betrayed him.
