The car overtook at least two cars and hit the island in the centre of the road on Friday night. After flipping several times, it had crashed into an oncoming van.
Tino Pipolua heard the crash from his kitchen and rushed out to help the driver of the van.
"I went to help but the police were already trying to help him so they asked me to stay back," Pipolua said.
"They were yelling at the occupants of the speeding car because they couldn't get into it. They were trying to keep them conscious."
Pipolua said firefighters arrived and cut the roof off the white sedan and ambulance staff got the injured driver out.
"I knew it wasn't good for the passenger because you could see they were not in any hurry to get him out," he said. "Then they covered him with a white blanket."
Pipolua, 40, a father of four, said it was common to hear speeding cars along the stretch of road and he feared for his children. He believed the car was going "motorway speed" in the 50km/h zone.
"Three months ago, a speeding car missed the corner and went into a house, so yes, I worry for my children," he said. "An innocent person could be killed so easily."
Nearby resident Armstrong Mahini also heard the crash and ran out to help. "I heard the high speed chase and then a big bang so I ran up the road."
Mahini filmed the aftermath on his phone and posted the footage to Facebook yesterday.
He spoke to the shaken driver of one of the cars the speeding car had overtaken.
Superintendent John Tims of Counties/Manukau police said the "senseless tragedy" could have been prevented had the driver chosen to stop when signalled.
"What we have now is one family coming to grips with the loss of a loved one and another sitting bedside in the hope their loved one will recover from critical injuries."
The matter has been referred to the Independent Police Conduct Authority.
A criminal investigation, which would be overseen by an independent police investigator had also begun, Mr Tims said, adding police would also carry out a practice and policy review.
