I believe Brian came home Sept 1. and told his parents that Gabby and he had broken up. He had a three day drive to come up with a story. Probably that Gabby took a bus to a friends house or something of that nature. His parents may have thought he seemed off but blamed it on sadness from the break up. They then tried to “cheer him up” with a bike ride and a camping trip. Around the 10th, or a couple of days before, Gabby’s parents start texting Brian. He tells his parents not to answer if they try texting them. His parents start to put pressure on him about where she is. Maybe then he gives another made up story like “I don’t know. She just took off.” They then contact a lawyer for advice. Meanwhile maybe Brian is threatening to hurt himself. He then takes off and the parents are scared he will do something if the police catch ip with him so they wait a couple of days.
Now the police can’t stop looking until they find him or his body. Because they have to be sure he isn’t out there on the run.
Having said all of that….
The second Gabby’s parents started calling I believe the right thing to do would be respond.
I, also as a parent, would be on tv telling my son to turn himself in.