Who kills the would be attacker with a knife in to kill a mockingbird

Bob Ewell is killed by Boo Radley. This happens on Halloween, when Jem and Scout are walking home from the pagent at school and Mr Ewell tries to attack them. Boo Radley sees what is happening and rushes out to save Jem and Scout. However, Heck Tate and Atticus do not want to tell the town what really happened, because dragging Boo into the limelight would be cruel after so many years of staying in his house. In the end they decide to say that Bob Ewell fell on his own knife.