Mr Pickett said the driver had climbed out of the cab of the truck to offload a shipping container. He was in the correct position to unload the trailer, he said.
"They have a remote control that controls the arms of the side lifter, he was in the correct position for off-loading it, but something has gone horribly wrong."
Mr Pickett said the trailer unit of the truck had tipped somehow and the man had become pinned between the truck trailer and a separate container on the ground.
Read more: Family's narrow escape from highway inferno
A contractor spraying weeds on the piece of land at the southern end of Totara St had made the call to emergency services, he said.
He was the only other person in the yard.
The man's body was still at the scene yesterday afternoon while investigators started their investigation, he said.
Scott Brownlee, chief executive of Coda Operations LP who own Priority Logistics, said everybody at the company was deeply saddened by the tragic event.
Mr Brownlee said many of the company's staff had been affected by the incident and their sympathies were extended to the family and friends of the truck driver.
"We have yet to determine the full details of the tragic accident. We will be giving our full co-operation to WorkSafe as we work to find out what has caused this devastating event to occur," he said.
We will be giving our full co-operation to WorkSafe as we work to find out what has caused this devastating event to occur.
A spokesperson for WorkSafe New Zealand said in a written statement that WorkSafe had been advised of the incident and an investigation had started.
"The initial notification to WorkSafe advised that a worker has been crushed between a truck and a container in Mount Maunganui. We were subsequently advised that the worker had passed away. This information is from the initial notification to us and may not reflect the actual circumstances which will not be clear until the investigation is completed."
WorkSafe could not provide further comment until the investigation had been completed, it read.