Answer: Bob Ewell is stabbed in the ribs. His killer used a kitchen knife.
Explanation: When Bob Ewell attacks Jem and Scout on their way home from the Maycomb Halloween festival, Boo Radley intervenes and saves the kids by fighting Bob Ewell. During the fight, Boo Radley apparently stabs Bob Ewell in the ribs with a kitchen knife, and Bob dies underneath the oak tree.