Someone had stolen cars from dealerships using a self-driving machine. He likely placed them during test drives
As they pieced the puzzle together, a plausible and coherent theory began to form in their heads. It became increasingly apparent that the person behind this scam was taking advantage of test drives at dealerships.
They could gain remote control of the car by installing these devices covertly during these short tests. They could then activate the device when darkness fell over the city. This would allow them to steal the vehicle without physically being inside.