Complex sentence: While Spring Break is occurring, a mysterious biker appears and begins to dispatch people when the back of his bike has a lever that when pulled combined with a button pushed by the biker causes the victim to undergo a treatment similar to the electric chair.
Split into simpler sentences: While Spring Break is occurring, a mysterious biker appears and begins to dispatch people. The back of his bike has a lever that when pulled (combined with a button pushed by the biker) causes the victim to undergo a treatment similar to the electric chair.