I think I’m beginning to understand why Boo Radley’s stayed shut up in the house all this time… it’s because he wants to stay inside. ” Said, Jem. Boo choice to stay in the house but, it seems only the ugly can drag Boo Radley out. When he sees, Bob Ewell attacking the kids. Boo Radley kills Ewell in order to defend the children. Heck Tate implies that Ewell fell on his own knife. Since there no way to know for certain who killed Ewell. Tate decides to “let the dead bury the dead”.
Scout walks Boo Radley home and takes a view in his shoes. “Boo was our neighbor, he gave us two soap dolls, a broken watch, a chain, pair of good luck pennies, and our lives. But, neighbors give in return. We never put back into the tree what we took out of it; we had given him nothing and it made me sad. ’’ Said Scout (Lee Chapter 31).
Boo Radley is a mockingbird because, he was shunned from society. But, still protected his children (Scout and Jem).
Boo Radley killed, Evil (Bob Ewell) to save and protect his children from him.