Complex sentence: Alone in his cabin, he composed a final letter to his wife Helena (with whom he has several children), blaming the defeat on his pride and arrogance, and then produced a small calibre firearm, which he used to commit suicide.
Split into simpler sentences: Alone in his cabin, he composed a final letter to his wife Helena (with whom he has several children), blaming the defeat on his pride and arrogance. DuGalled then produced a small calibre firearm, which he used to commit suicide.