Atticus is a humble man, and he doesn't like being fawned over. He isn't prideful, and he doesn't want people to shout his accolades in front of his children. That's just the way he is..... We can infer that he would have finished the sentence with something like, "the best shot in the county."
"What’s the matter with you, boy, can’t you talk?" said Mr. Tate, grinning at Jem.
"Didn’t you know your daddy’s—"
"Hush, Heck," said Atticus, "let’s go back to town."
To Kill a Mockingbird