why was karim angry?

As the violence in the city worsens, school is canceled, and Karim spends his time with his friend Béchir and his crush Nada. Eventually, Béchir's family flees to Paris out of concern for their safety. Karim stays because he is in love with Nada. However, one day Karim goes by Nada's house only to discover that a bomb has destroyed her building and killed her. Her little sister, Maha, and their baby brother, Jad, are the only survivors of the Tabbara family.