Radio host Simon Barnett pulled an injured woman from the wreckage of a car which crashed in front of him and his family, cutting his hands on shattered glass as he did so.
Barnett witnessed the two-car collision while travelling with his four daughters and two of their boyfriends on State Highway 5 just after 1pm on Friday.
The group were on their way to Taupo to meet Barnett's wife Jodi whose sister had died, aged 37, so were already feeling "pretty emotional", he told the New Zealand Herald last night.
About 20 minutes north of the town, while driving behind a Hyundai iMax, a silver car in front of both vehicles pulled to the left and for "no apparent reason" did a U-turn, Barnett said.
"It was horrible ... I thought 'oh my god, this woman is turning into the path of another car'. I felt sick. The other car went right into the side of her. You don't forget that sound. It's just awful."
He instinctively swung his left arm out to protect his youngest daughter, 16-year-old Lily, while avoiding the crash, Barnett said.
Emerging from his car he could hear a woman screaming, children crying and a stuck car horn blasting.
Shattered glass was everywhere, the cars were steaming and air bags had been deployed.
The air was thick with a smell he likened to that of gunpowder.
"It was just as you would imagine it to be - ghastly. I'll never forget it."
Looking towards the car he could see the outline of two carseats and yelled back to his own children, trailing behind him, to stay back.
He was afraid what they might find, Barnett said.
A woman trapped by her seatbelt in the silver car was screaming "get a knife, get a knife", so he retrieved one from a campervan, ignoring a cut to his fingers received while trying to pull the woman free.
"She kept saying 'I'm so sorry, I'm so sorry' ... she kept hugging her kids. They were two girls aged about seven and three. One was crying 'I want to go home'."
The gunpowder smell had him rattled, Barnett said.
"It went through my mind 'imagine if this thing bursts into flames'."
Next to the silver car, those in the Hyundai - what appeared to be an extended family of eight - looked "completely bewildered".
A police spokesman said all of those involved escaped injury, and investigations were continuing. But Barnett said the woman in the silver car went to hospital.
The woman recognised him, as did the driver of the car, the longtime DJ said.
"The ambulance driver said to her 'is that your husband?' and she said 'no, that's Simon Barnett'."
He was embarrassed by the attention, as many people helped in the aftermath of the crash, including the "amazing" emergency services.
A police officer later called him to say the woman had been discharged from hospital the same day suffering only from bruising, Barnett said.
"They were all just so lucky."