Taupo man Tony Duffy,45, who is also a volunteer firefighter and an ex-police officer, said his training kicked in during the dramatic rescue.
He was driving a truck-load of bread to Palmerston North when he was the first to arrive at the "horrific" debris-strewn crash scene on Saturday afternoon.
The head-on collision occurred on State Highway 3 near Sanson, police said. A car lost control and veered across the double-yellow lines directly into the path of an oncoming SUV towing a horse float
The driver of the car, Kent James Bond, died at the scene and the SUV and horse float jack-knifed and rolled, trapping a 41-year-old woman and three children in the vehicle, which then caught fire.
Mr Duffy reached the destroyed car first and initially didn't think the driver was inside but then saw him in the passenger footwell.
He checked for the driver's vitals and realised he was deceased, before moving toward to the SUV, where another man had started working to free the passengers.
Smoke was already billowing from the vehicle and flames were starting to creep out of the bonnet.
Two passengers had already been pulled free but the other two, who were young girls, were stuck inside, he said.
"I was trying to reach in and help them...grab a knife, cut the seatbelts. It was all crumpled up so we couldn't really get them out.
"I looked up and I saw the flames starting to get quite big and I thought if I don't try and subdue that somehow then we're not going to get them out," he said.
The volunteer firefighter yelled for fire extinguishers from any of the nearby vehicles and five people came forward with them.
It was just enough to keep the blaze under control before the two girls were cut free and dragged to safety.
But there was more work to be done - a banging from the trailer alerted the rescuers to a horse that was trapped inside.
Mr Duffy broke the metal bar restraining the horse, which then bolted outside and immediately put its head down to graze, he said.
The whole rescue took just 10 minutes.
Mr Duffy said he was the right man to be first on the scene - he is a volunteer firefighter in Kinlock and was in the police force for 12 years before becoming a truck driver seven years ago.
"With my background and training I didn't really think about it until after, you know. It's just doing my job. I wouldn't say I was a hero, just the right place at the right time I guess," Mr Duffy said.
"Everyone did their part. I've seen that scene a few times. But it's not often that it literally happens right in front of you. You're doing your job and driving and then all of a sudden the whole thing just changes in seconds."
Resident Tracey Doyle, who lives on a farm near the crash, said she heard the vehicle explode.
It was an extremely close call for the passengers and the horse, she said.
"There was a big explosion we heard and it went up in smoke, if they hadn't pulled them out I would say there would be a different story today. They are heroes," she said.
Acting Inspector Nigel Allan said preliminary investigations suggested the car driver had overtaken a number of vehicles in the passing lane before losing control.
Excessive speed was indicated to be a factor, he said.
The men who pulled the passengers free almost certainly saved their lives, he said.
"While this is an absolutely tragic crash, I have no doubt the selfless and heroic acts of those persons who came to the assistance of the people trapped in the burning vehicle have saved four lives," Mr Allan said.
The 41-year-old woman was still in a critical but stable condition last night and the three children were stable in the children's ward, a Palmerston North Hospital spokesman said.
By Lauren Priestley of NZME. News Service
