How is the end of chapter nine a turning point in The Kite Runner?

The end of Chapter Nine in "The Kite Runner" is a turning point as it marks the beginning of the end of Amir and Hassan's friendship. It is when the pivotal event of Hassan's assault by Assef occurs, and Amir's inaction and subsequent guilt deepen the rift between them. This event sets off a chain of consequences that lead to significant developments in the story's plot and characters.