Complex sentence: Genie's father already had difficulty controlling his emotions, and his mother's death deeply affected him; because she had been walking with her grandson Genie's father viewed his son as responsible for what had happened, which heightened his anger.
Split into simpler sentences: Genie's father already had difficulty controlling his emotions, and his mother's death deeply affected him. Because she had been walking with her grandson Genie's father viewed his son as responsible, which heightened his anger.