If they were sent specifically to his address they had every right to look in those cars. They have to protect themselves and for all they know there could be someone in one of those cars. If they weren't sent specifically to his address then they shouldn't have been in the driveway looking in the cars but they didn't harass anyone. Maybe there has been some vehicle break-ins recently. If someone knows how to use a slim-jim properly you can be in the car in seconds toss the vehicle grab the goodies and close it all back up looking in the window they would see if the car had been tossed.