Matt Albert-Wihone told the Herald that he was driving to work around 7.30am when he saw a man jump from a moving vehicle - before sprinting off the bridge and jumping into the water.
"We were on the way to work on the bridge.
"Just before you reach the high point in the bridge, the back door of the car flew open then and he just stepped out like it was stationary.
"This was at 80kmh, he took a few tumbles on the side of the road and before we had time to stop he was off. He was up straight away and without hesitation, he just jumped [off the bridge].