how does karim betray them and what is babas reaction? chapter 10

When the refugees finally reached Karim's brother's house in Jalalabad, he told them that his brother, Toor's, truck had broken the week before and could not take them to Peshawar, Pakistan. Baba smashed Karim against the wall and began to strangle him, furious that Karim had lied to them in order to take their money.