Auckland dentist Dr Jacky Lam, an ex-St John first responder, arrived minutes after the crash and worked with emergency services and a trainee nurse who was at the scene to try to save the man's life.
The man was wearing his seatbelt but looked like he had received quite a "strong impact" in the crash, Lam said.
"I have seen some things like that, but never that bad. The car that hit him must have been going very fast."
Police cut the seat belt and they managed to pull the unconscious man out of the car and performed CPR for several minutes, but could not revive him.
"It is such a tragedy. This man was out enjoying the day, doing nothing wrong, waiting at the lights and then this happened, just gone, it could be any one of us. It has damaged a family's life too."
Lam said the driver of the car who crashed was conscious but seemed dazed. He was stuck in his crushed vehicle and needed the roof to be cut off by firefighters to free him.
Inspector Cornell Kluessien said three cars - an SUV, a four-wheel drive and a wagon - were waiting at the lights on Botany Rd when the third car was rear-ended.
"The last car came up at high speed and ran into the back of the third car and shunted all three of them forward," Kluessien said.
"The person in the third car died, a single occupant and the person in the last car - that hit them - was trapped initially, and had to be removed by the fire brigade."
The person in the fourth car, a Holden sedan, was removed from the car and taken to Middlemore Hospital.
The police Eagle helicopter also attended the scene, landing on the road and picking up a police photographer who took aerial photographs of the incident.
Anybody who observed the crash or had footage could contact Constable Graham Mako, Counties Manukau Serious Crash Unit, on 021 192 0746 or email Graham.Mako@police.govt.nz.
