Parsons estimated the driver of the red ute was going about 100km/h.
Parsons said about 1km further down the road he noticed a white Hyundai pulled over on the shoulder of the road.
"He must have clipped him," he said.
The Aucklander said it wasn't until the pair arrived home that he realised how serious the outcome could have been.
"We could have been killed."
Police managed to stop the vehicle after the Eagle helicopter spotted it shortly before 4pm.
A police spokeswoman told the Herald the Eagle followed the car as staff on the ground rushed to stop it.
"We deployed road spikes and stopped it in Onehunga.''
No one - including the driver - was injured.
A man in his 20s is expected to face charges.