This is what I IMAGINE happened, applying Occam's Razor....
In this part of the country, peoples "Driveways" are not 10 feet long from the busy public road in the front of your house to your front door where you can clearly see a FedEx package waiting for you and the distance between you and your "visitor" is at most, 10 feet. Instead, people's "driveways" are mile-long private roads maintained by a local community of property owners along that private road. Such a road is often gated. It is uncommon to see strangers there, and without invitation, might even be posted as trespassing.
So, this father and son are returning home, turning onto their private road, where this UHaul rental truck (with a tiny little magnetic FedEx sign stuck on somewhere invisible) driven by a stranger is attempting to drive out.
This appears to be a robbery, so the father and son block the road to ask the driver what he is doing. The driver , rather than roll down his window and say "howdy boys.. FedEx here" and gesture to wherever the embelum was stuck on... or flash an employee badge or someting... instead chose to ignore them and drive around them and leave.
What followed was a road-rage-esque pursuit that ended with the father and son eventually having an oh shit moment as they realized what they were doing, and surrendered themselves to Police.
That's my GUESS.
Let's see if we get a reliable play-by-play and see how close this was.