To Kill a Mockingbird:

Despite Tom's conviction, Bob Ewell is humiliated by the events of the trial, Atticus explaining that he "destroyed [Ewell's] last shred of credibility at that trial." Ewell vows revenge, spitting in Atticus' face, trying to break into the judge's house, and menacing Tom Robinson's widow. Finally, he attacks the defenseless Jem and Scout while they walk home on a dark night after the school Halloween pageant. One of Jem's arms is broken in the struggle, but amid the confusion someone comes to the children's rescue. The mysterious man carries Jem home, where Scout realizes that he is Boo Radley.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who attacked Scout and Jem?
Bob Ewell