Loading and Unloading of Vehicle

A customer was injured on our insured's lumber yard while he was there to purchase some wood. An employee of the lumber yard was loading the wood into the customer's car. The customer was standing behind the car at that time and was not involved in the loading of the wood at all. When the employee had completed the loading of the vehicle, he was closing the hatch of the station wagon when he struck the customer in the head with the hatch of the car.

We are submitting the claim to the insured's CGL carrier, but one of our associates has asked an interesting question: can the employee be considered an insured under the customer's personal auto policy since he was “using” the covered auto at the time of the accident? The auto policy does not define “using,” but other insurance policies consider loading and unloading to be use of a vehicle. Can the employee be an insured under the customer's auto policy and so, find liability coverage there for the injury?