Tim Johnson was a dog owned by Mr. Harry Johnson who drove the Mobile bus and lived on the southern edge of town. Tim is described as a liver-colored bird dog and "the pet of Maycomb". In chapter 10, the Finches see Tim sauntering down the street acting strangely. They notice that he is probably sick. As he gets closer, they see him wobbling and they realize he has rabies - they call him a "mad dog." Atticus is forced to kill the dog because he is a danger to the community. Scout and Jem are astounded to learn that their father is a crack shot as he fells the dog with one shot. Miss Maudie tells Jem and Scout about their father's skills and points out to them that truly great people are humble about their skills. Scout and Jem both learn something about their dad in this chapter - that he may be 50 but he is far from feeble. They will soon learn about his other strengths.
Tim Johnson is certainly one of the most unusual characters in Harper Lee's novel To Kill a Mockingbird. He makes only one appearance (in Chapter 10), and it turns out to be his last. Tim is a "liver-colored bird dog" who is familiar to the families that live near the Finch house. However, in Chapter 10 his abnormal walk and actions are quickly perceived to be a case of rabies. Atticus is called upon by Sheriff Tate to do the dirty work, and "Old One-Shot" makes his return and lives up to his nickname, dispatching of poor Tim with one bullet to the head. It is one of the most interesting chapters in the novel (and the movie). Tim was owned by his master, Mr. Harry Johnson.