The accident came just five hours before a fatality-free end to July for the Waikato district.
Eyewitnesses said the car that ran the give way sign was catapulted 25m from the point of impact, flinging the two occupants to the front lawn of a Rolleston St home. The car ended up on its roof in the front yard of a neighbouring house.
Witnesses said the car failed to stop at a give way sign and was hit by a car travelling through the intersection of Rolleston and Whitmore Sts.
Resident Peter McCullough said he heard a "bang". He added: "I thought 'hell, that sounds like an explosion'.
"The cars are all over the place. They ended up on the lawn. I could see the two bodies were still lying there covered up. It looks like the white car with the four [people] in it failed to stop at the give way sign. The impact of the car was huge - there was nothing much left of the badly damaged car. It was bloody awful. The white car was a mess."
Neighbour Martin Jones said he rushed to help.
"On the lawn one guy was getting CPR but he died. Others were helping another guy but he died while they were doing it. Now the neighbour has two bodies on their front lawn plus a car on its roof."
Jones said all the car doors were jammed and he ran to get tools to force them open when emergency services told him to wait for help.
The driver of a passing vehicle saw the crash and told Jones the car travelling down Rolleston St did not stop at the Whitmore St intersection.
"They said the car just drove straight through the giveway sign. The other car didn't have a chance to stop in time and crashed straight into it.
"Normally we would hear the noise of the brakes screeching but we didn't hear anything, just the bang."
Waikato road policing manager Inspector Leo Tooman said the accident came just five hours before the region would have had a "fatal-free" July.
One occupant of the second car, who was named Michael Vincent, was taken by ambulance to Waikato Hospital.
The day of tragedy began at 7.40am with a head-on crash with a truck on the Desert Rd. Those who saw the accident scene described the remnants of the car as resembling a "scrunched up" piece of paper.
The accident scene was so confused and debris so far spread that police initially had no idea how many people were in it. State Highway 1 between Waiouru and Rangipo was closed for seven hours.
A southbound Toyota went under the truck in icy conditions, but police said the cause was to be determined.
Two men, believed to be in their 20s and from Auckland, were in the Toyota and died at the scene.
The truck driver, a Palmerston North man, was unhurt.
Waiouru deputy fire chief David Murray said: "The car was unrecognisable as a car except for the engine bay. The guys likened it to a piece of paper being scrunched up.
"Basically the car had been cut in half. The cabin from the firewall forward was sitting on the road."
The firefighters helping out were mostly young, Murray said. "They knuckled down and got the job done, but we'll continue to monitor their state of mind. It's a very nasty job but we've got to do it."
At 8.20 last night, a motorcyclist was killed in Christchurch after hitting a pole in Moorhouse Ave, scene of a triple fatality three weeks ago, when a car fleeing police crashed. Staff at a nearby McDonald's said diners heard the motorcyclist hit the pole.
Auckland's Tamaki Drive was then closed after a serious early-hours crash which saw one person cut from damaged vehicle.
