What did Atticus do in Chapter 9 that changes the children's opinion of him?

The children actually see their father in a different light in Chapter Ten, when he successfully shoots the rabid dog Tim Johnson, and the children find out that their father is the best shot in the county.... "One-Shot Finch".

From what I've seen, he has shot a rabid dog 🐶. From the children's opinion, I suppose they think there is the evil or bad side of Atticus Finch. As Jill D said, the children found out that Atticus was the best " one shot Finch ". They've found the actual truth of Atticus due to rumours.