During breakfast the night after the mob shows up at the jail, Atticus compares the men with “a gang of wild animals”. One of the reasons he does this is to highlight the mentality of a mob. When you think of a pack of animals, you think of them acting as one organism. Think about a pack of wolves bringing down an elk or a pride of lions attacking a zebra. They have one purpose, and work together for that purpose. The mob of men came to the jail with one thing in mind - to harm Tom Robinson, and they weren’t going to let anyone get in their way, not even Atticus, who is a respected member of the community. But Atticus also highlights the fact that a mob is still made up of people, and that by connecting with just one person the way Scout did with Mr. Cunningham, a mob can be stopped. He helps the children see that even though a mob is a scary thing, it can be thwarted by reminding those “animals” of their humanness.
Lee, Harper. To Kill a Mockingbird. (Soft Cover). Perennial, 1961