4 He heard muffled screaming and saw the boot of the car rattling.
When he saw it, he thought someone is trapped in boot of the car and crying to get help. He couldnt see exactly as it is dark. But as he get closer to the car he was sure the screams coming from the car.
5 He rushed up to the car pulling his dog with him
He thought he can help the person who is in danger. But when he opened the boot, he saw a woman staring at him.