Ishmael Beah ends with the story of the hunter and the monkey to leave his audience with a vivid image of sacrifice and a lesson on how to end repetitive violence. It leaves a lasting image in a reader's mind and drives home the moral of the stories he's shared from his life.
The little boy is faced with an awful choice. If he kills the monkey, his mother dies. If he doesn't kill the monkey, his father dies. It feels like an impossible choice to make for someone who doesn't want to lose either parent. However, for Beah, there was a choice to be made even when he was a little boy. He had a logical answer that made sense to him.
The monkey is the thing creating the choice. It is the reason that one of his parents will die. If he does nothing, he loses a parent. But if he kills the monkey, he loses a parent—but the monkey can never put another hunter through that again. Because the monkey is creating pain and discord, Beah believes he can stop that cycle simply by killing the monkey.
Sometimes impossible choices and harsh deeds are needed to stop unending violence. People fighting that kind of perpetual cycle will lose something they love as the price for stopping it. It's scary and harsh, but that's the kind of reality that Beah grew up in as a child soldier. As he grew into an adult, he was better able to comprehend the forces at play.