Complex sentence: He kills Ted by stabbing him in the back of the head then crushes Doug's head against the shower stall after Sara moved into their room to get dressed for bed, she changes her mind and comes back, finding Doug dead.
Split into simpler sentences: He kills Ted by stabbing him in the back of the head then crushes Doug's head against the shower stall after Sara momentarily leaves for her room to get dressed for bed. She changes her mind and comes back, finding Doug dead.