Rahim Khan gives amir a letter from Hassan, who wrote it six months earlier. what is the tone of the letter? how does Amir react? why is this scene signifficant?

After Rahim Khan finished telling the story about him and Hassan, he handed Amir a letter and a photograph. The photograph was of Hassan and Sohrab. In the letter, Hassan described the violence and injustice in Afghanistan. One day, Farzana spoke slightly loudly in the market and a Talib beat her so hard that she fell down and was bruised for days. Despite the terror, Hassan said, Sohrab was a healthy and smart boy; Hassan had made sure he was literate and knew how to shoot a slingshot as well as his father. Hassan ended his letter by expressing his wish to see Amir in Afghanistan again. Rahim Khan explained that the letter was written six months before. A month after he had arrived in Peshawar, he received news of Hassan's death from a friend. After he left Kabul, word spread that a Hazara family was living alone in Baba's house. One day, the Taliban came to the house and demanded that they leave. When Hassan protested, they took him out to the street, forced him to kneel, and shot him in the back of his head. Farzana ran out screaming and they shot her dead as well. The news devastated Amir, who could only whisper, "No. No. No."

You might also want to check out Gradeesaver's analysis for this chapter. I have provided the direct link below.

http://www.gradesaver.com/the-kite-runner/study-guide/section6/