Complex sentence: Cooke would steal a car almost every night, returning it before the owner awoke and it was later discovered that the cars involved in several hit and runs had been returned without the owners realising they had been stolen.
Split into simpler sentences: Cooke would steal a car almost every night, returning it before the owner awoke. It was later discovered that the cars involved in several hit and runs had been returned without the owners realising they had been stolen.