Chapter 10 of To Kill a Mockingbird concerns Jem's and Scout's worries that their father is "old," "feeble" and unmanly. Atticus responds to Jem's request that they play tackle football with what becomes a standard " 'I'm too old for that, son.' " (This is the response he gives later when Bob Ewell demands to fight.) Although the children never discuss Atticus' supposed failings with him, they bring up the matter with Miss Maudie, who assures them that Atticus has " 'life in him yet.' " When Atticus arrives at the scene of the mad dog, Tim Johnson, staggering up the street, Sheriff Tate quickly recognizes the right man for the job. He well remember's Atticus' marksmanship skills as a youth and thrusts the rifle at him. Atticus' humility is evident.
"I haven't shot a gun in thirty years--"
But he takes the rifle and proceeds to put down the dog in one shot. However, his initial reluctance probably has nothing to do with the rustiness of his skills: He knows that Jem and Scout are watching, and he is not comfortable with them knowing this side of his past. He is also a humble man, and he doesn't consider his talent worth of accolades. When Maudie calls him by his old nickname--" 'I saw that, One-Shot Finch' "--Atticus glares at her. When Heck begins to tell the children about their father's marksmanship skills, Atticus tells him to " 'Hush.' "
It becomes clear that Atticus is not as feeble as his children believe, but the scene also shows his humility concerning his skills. Killing is not a talent, nor is it a something of which to be proud. Jem recognizes this strength at the end of the chapter when he tells Scout not to brag about it at school.
"Atticus is a gentleman, just like me!"