Complex sentence: Enraged about his car, Hi-Hatz threatens them with a gun, refusing to believe their story of aliens-until his henchman is attacked by one, allowing the gang to escape.
Split into simpler sentences: Enraged about his car, Hi-Hatz threatens them with a gun, refusing to believe their story of aliens. However, his henchman is suddenly attacked by one, distracting Hi-Hatz and allowing the gang to escape.