What encounter does Margery have in the Prologue, and how does she handle it?

Clem McCullough bothers Margery when she is delivering books. He has a rifle that is cocked with his finger on the trigger. He tells her to get off her mule and he points the rifle in her face. She can tell that he has been drinking. She grabs a heavy book and smacks it into his face. The rifle goes off and he drops. Margery urges her mule down the crick bed, not looking to see if McCullough is following.