The truck and trailer unit had big bins on them, he said.
However, he was not sure what type of truck it was or the company it belonged to.
The driver left, making a left-hand turn out of the information carpark, heading north.
It was then Mr Wihongi spotted a dark form on the ground and went for a closer look.
"At first I thought it was a dog just sleeping on the ground. But then I saw it was a guy. He was making huffing, wheezing noises.
"I knew straight away I couldn't do much for him and rang 111 and asked for the ambulance," he said.
Fellow workmate Rob Tevita met up with Mr Wihongi outside the centre shortly after the grisly discovery.
Mr Tevita said the man was face down in a pool of blood, his clothes ripped.
"I was talking to him to see if there were any signs of life and trying to get a response but there was none. There wasn't much the ambo guys could do when they arrived," Mr Tevita said.
Police made an appeal for information about the truck trailer which had been parked overnight in the carpark at the centre, just south of the city.
Whangarei police Senior Constable Paul Nicholas said it appeared a man had fallen asleep beneath a trailer unit at the centre. It was thought the driver returned early yesterday and hooked up to the trailer and drove off, unaware of the person beneath.
Mr Nicholas said police wanted to speak to the driver or anyone who may know who the driver was, or information about drivers who parked at the centre regularly. The deceased had been identified but family members were still being advised before police released his name.
Yesterday's death brought Northland's road toll to five just ahead of a busy Easter weekend on the region's roads.
