Why does Walter Cunningham leave Tom Robinson at the jail?

In Chapter 15, the Old Sarum bunch travels to the Maycomb jailhouse to lynch Tom Robinson. However, Atticus is waiting outside of his cell when they arrive. The Old Sarum bunch encircles Atticus, and they try to convince him to leave. Suddenly, Scout runs into the middle of the group out of nowhere. She does not realize the dangerous situation she has just entered and recognizes Walter Cunningham. After Jem and Dill follow Scout out of their hiding place, Atticus tries to get Jem to take the children home. Scout then attempts to get Walter Cunningham's attention by asking about his son and commenting on his entailment. Walter initially ignores Scout, but then acknowledges her after realizing the difficult situation Atticus is in. Walter has empathy for Atticus and views the situation from his perspective. Walter then speaks to Scout and tells his men to go home. The reason he decided to call off the lynch mob was because he understood the difficult position that he had put Atticus in.