Complex sentence: Dominic Caruso, his brother, is an FBI agent who, while investigating a kidnapping of a little girl, finds her in a tub raped and killed, and he kills the suspect in self defense after the suspect threatens him with a knife.
Split into simpler sentences: Dominic Caruso, his brother, is an FBI agent who, while investigating a kidnapping of a little girl, finds her in a tub raped and killed. Caruso kills the suspect in self defense after the suspect threatens him with a knife.