Why doesn't Joe share the information that he has about his mother's attacker with the people who love him?

The Round House, written by Louise Erdrich, is a novel written from a thirteen-year-old Native American boy's perspective. Joe, the main character of the novel, learns that his mother, Geraldine, has been brutally attacked, and he must deal with the aftermath of this attack. This attack and finding the person responsible gets more complicated due to differences in the federal law processes and the Reservation law practies, as well as the fact that Joe's mother cannot remember where exactly the attack took place.
When Joe first discovers that his mother's attacker has been arrested and put in jail, he and his father are both relieved. However, due to the fact that Geraldine does not know exactly where this attack took place and to the change in legal jurisdictions between types of law, the attacker is released.
Joe, being a protective thirteen-year-old boy, wants to help his mother escape from the fear that has taken over her life because of this attack. Joe begins doing research on this man and decides not to share any of the information with the people he loves for multiple reasons. One reason that Joe does not want to share this information with anyone but his best friends is because he does not want to get in trouble with his father. Joe has been eavesdropping on his father's conversations about this attack and has been warned to leave the situation alone. Another reason that Joe does not want to share this information with his family is that he wants to take care of this matter on his own to prove that he is growing up. Joe knows that his mother is still afraid and decides to take matters into his own hands.
A third possible reason that Joe doesn't want to share any information about his mother's attacker is his own guilt. While Joe is searching for details about his mother's attack, he finds a gas can, beer, and an old doll. Inside the doll, Joe finds 40,000 dollars, which he puts away in college funds. When an FBI agent visits his house, Joe tells the agent about the gas can and beer he and his friends found, but he does not tell them about the doll or the money—two important clues that would have helped solve this mystery.
Joe and his father go grocery shopping one day and run into Geraldine's attacker at the store. When Joe's Father, Bazil, goes after him, he has a heart attack and must go to the hospital. Geraldine, upset that this attacker has now hurt another member of her family, makes statements to Joe that make him think she is going to try to kill the man who attacked her. Joe does not want this man to continue to affect his family and decides to follow through with his own plans.
After his mother's attacker has been killed, Joe begins to feel that he "has a monster inside" of himself. He feels guilty and has nightmares of all the crimes he has committed. Overall, Erdrich captures the mindset of a thirteen-year-old boy quite well and is able to write her story entirely from Joe's perspective.