I said in the beginning i thought that (MOO) A neighbor heard the scream an hour after the original abduction, neighbor either called the brother or came over and said I heard screaming is everything ok.. brother probably as he peeked outside while on the phone or looked outside when answering door then saw Holly's car, investigated further and found the blood. At that time either the neighbor and the brother called 911 OR the brother called his mom and the mom and brother both called 911.
Another scenerio
Brother goes to leave himself and realizes holly's car is still there investigates further.. sees the blood and calls his mom and mom and brother both dial 911.
Neighbor heard the scream and attributed it to a rabbit being killed or a loon or some type of bird that have screams and then when she saw the neighborhood canvas or saw cops she thought.. UHH OHHHH and went and then told them she heard screams at such and such a time.