The grieving family of the seven people who died in a horrific crash near Picton on Sunday are in disbelief after losing their whānau in the blink of an eye.

Immediate and extended family, along with friends, are gathered at the family home in Pukekohe, awaiting news about one of the crash's two survivors, who is currently undergoing surgery after being placed in a coma.

Speaking to the Herald, 21-year-old David Lagud was still in shock while he talks about his much-loved family members who died driving north on State Highway 1 towards Picton yesterday when the van they were travelling in collided with a truck about 7.30am.

Among those dead were married couple Paul and Diseree Brown, 61 and 48, and their youngest son Mark, 14.

Diseree's sister Divine Dolar, 56, and Divine's daughter Flordeliza Dolar, 19, also perished.

Two of Diseree's sons who also travelled - Pedro Clariman, 26, and Luie Lagud, 16 - survived but the latter was in a coma and undergoing surgery this afternoon after suffering significant injuries to his spine and head.

Diseree had three other children who did not travel - David, Princess and Joanna.

Tragically, Pedro's partner died in the crash, along with his daughter Mika, who was only 9-10 months old.

The collision, which left the van completely destroyed, was the most deadly incident on New Zealand roads since April 2019 when eight people died in a head-on crash near Taupō.

The nine family members had travelled to Dunedin from Auckland in a length-of-the-country road trip - in a Toyota Hiace van - to farewell Paul's aunt who had recently passed away. The funeral was held in Gore last week.

The scene of the crash on State Highway 1, south of Picton. Photo / George Heard

They left Dunedin on Saturday afternoon and stayed overnight with a friend in Christchurch before continuing their journey home, leaving at 2.30am yesterday so they could make their ferry crossing to the North Island.

David hadn't gone on the trip because he had to work at the local Pak 'n Save supermarket in Pukekohe and also because he suffered from motion sickness.

He last heard from Pedro's partner on Saturday night, asking him to feed the bird.

He also missed a call from Paul - his stepfather - on Saturday night. Paul later texted David asking him to clean the house prior to their expected arrival home late on Sunday night.

That was the last contact David had with his family prior to the crash.

"It's just shocking, to happen that fast," David said.

"In a blink of an eye, it's all gone."

David had spoken to his brother Pedro since the crash, who was being supported by his two sisters while he and Luie were in Wellington Hospital.

David said Pedro had minor injuries and was able to walk, albeit with difficulty.

According to Pedro's account told to David, Pedro had been driving when the family left Christchurch, allowing Paul - in the front passenger seat - to sleep for almost four hours in addition to the rest he got in Christchurch.

After that, Paul swapped with Pedro to drive the rest of the journey to the ferry.

Paul was reportedly well-rested when he took the wheel, David said.

Before falling asleep after his stint at the wheel, it's understood Pedro had some time playing with his baby Mika.

The aftermath of the crash. Photo / George Heard

Asleep at the time of the crash, it's believed Pedro woke up to a scene of carnage and tragedy.

"He saw my dad's body on the road and then my brother Luie, he was awake and then he collapsed," David said.

"Then the next minute, the helicopter was there, taking my little brother to the hospital."

Early reports suggested the van had crossed the centreline before hitting the truck.

The family, however, contest this and are eager to see the result of an investigation.

David said his brother Pedro was grief-stricken after hearing his partner and child were dead.

"He was devastated, he was crying a lot.

"Both of his loves are gone."

Diseree and her children, originally from Quezon City in the Philippines, moved to New Zealand about seven years ago.

Divine, along with her partner and Flordeliza - nicknamed Apple, made the move about three months ago and had been staying with Diseree while their visas were processed.

Divine's partner, who was at the Pukekohe home, was wracked with grief when the Herald visited, mourning the loss of his partner and child, along with members of his wider family.

The road trip south was billed as a sight-seeing tour for the mother and daughter, who were reportedly excited to see the country.

Diseree was a fan of Facebook lives, David said, and had posted some footage of their journey so the family could see.

Seven people died in the horror crash. Photo / Supplied

The group had been especially excited to visit Queenstown and witness its majestic landscape.

"They were so happy," David said.

"They had good memories before they died."

It wasn't the first time they'd attempted the same distance. About five years ago, the family - including David - had driven to Dunedin to visit Paul's mother and navigated the journey without incident.

While Paul wasn't their birth father, David said he and his siblings were very close to him ever since he and Diseree met.

David said his parents were consistent church-goers, attending the local Elim Church every Sunday.

Paul was a teacher while Diseree worked for Turners and Growers, but also operated a clothes selling business on the side.

"They were nice people, they might be strict but they're good people, they cared about their children."

Speaking from the dining table, David cast his eye towards a computer screen in the lounge where his younger brothers Luie and Mark would play games.

The pair, Pukekohe High School students, also took part in the church as members of a youth group.

David said they were very close, almost like twins.

David, other relatives and friends were currently waiting for news of Luie's surgery, taking place this afternoon.

The cars of his family still sat in the driveway.

Luie had been awake at some point last night before going into a coma, giving the family some hope.

It was expected he would remain in Wellington for the coming weeks.

The bodies of those deceased were set to be transported from Christchurch to Auckland later this week.

Having experienced such loss and with his brother's life in the balance, David urged people to cherish time with loved ones.

"Spend as much time with your family, friends," he said.

"You never know what's going to happen next, just like that, it's all gone."

The former principal of Parkside Specialist School in Pukekohe, Judith Nel, told the Herald she had employed Paul more than a decade ago.

She said he was a primary teacher who received extensive extra training for the high needs children the school dealt with.

He performed in his role and was a respected educator, Nel said.

"Paul proved himself to be a very caring and competent teacher."

Paul had children with his first wife and years ago had married again to Diseree a "lovely, gorgeous Filipino woman", Nel said.

He studied primary education at Dunedin Teachers College.

Parkside, in the southern Auckland town of Pukekohe, caters to high needs pupils aged 5 to 21.

It is nationally recognised for its work with students who "fall into the broad categories of profound, severe and moderate disability", its website says.

*Additional reporting George Block