Complex sentence: One year before the murders the family home had been invaded and items and cash were stolen from Andrew's bedroom; from then on Andrew had become paranoid and insisted on locking all doors (including those inside the house) even when someone was at home.
Split into simpler sentences: One year before the murders, the family home was broken into and some items and cash were stolen from Andrew's bedroom. Andrew became paranoid and insisted on locking all doors, including those inside the house, even when at home.