Complex sentence: Witnessing the bullies picking on two teenage boys on a nearby hill while they are sledding, Billy decapitates the bully's head and his severed head comes rolling away who's body is discovered by the other bully who runs away screaming.
Split into simpler sentences: Witnessing the bullies picking on two teenage boys on a nearby hill while they are sledding, Billy decapitates the bully's head and his severed head comes rolling away. His body is discovered by the other bully who runs away screaming.