There were two rottweilers in the car at the time of the crash as well, who were rescued by a bystander. The dogs are being treated at the vet, one for a broken leg that may need to be amputated.
"I've got a little bit of what happened but I'm not too sure, it's not really my place to say ... but it was an uncalled-for accident," Tepihi said.
The family was "pretty cut up", especially as the loss comes just before Christmas. Another relative is flying over from Australia and the family will now start to figure out "the costs involved with everything".
They would let Colin and the teenager "heal for a bit" before breaking the news of Wendy's death to them.
Tepihi said he felt "destroyed", but felt he had to be strong for the family.
"She was a strong lady, a rock to our family, so someone has to step up now."
Wendy had been a social worker for the past 15-20 years and had many kids from Child Youth and Family come through her care, some of which she raised herself, he said.
The boy involved in the crash was one of those children.
"She was just a big heart, generous person. Yeah, she just toddled along doing her thing, touched a lot of people along the way and it's just terrible that she was taken away from us in such a needless fashion."
Tepihi said there had been "a few crashes" on the road south of Levin, but he was "not sure if it's just a bad stretch of road or just bad people driving or bad luck".
The family are thinking now about raising money for the vet bills, and will need to see whether the injured dog must have its leg amputated, or whether metal plates can be put in.
It was "tragic" the family had lost one loved one, but they were thankful Colin, the teenager, and the two dogs had survived.
Tepihi wanted to thank the emergency services that came to the scene of the crash, as well as the mystery bystander who pulled the dogs out of the car wreck.
"Be careful on the roads," he said.
"One mistake can ruin a family."
There have been three crashes on that stretch of road in the past 24 hours - two of which were fatal.
About 7km south of the first incident, which happened about 5pm, another person died in a separate crash, about 7.10pm.
The second incident involved a car and a truck and occurred north of the intersection of Waikawa Beach Rd and SH1.
Both crashes forced emergency services to close SH1 and detours were put in place.
There have been 343 deaths on New Zealand roads so far this year, compared to 338 for the same time last year.
Tepihi has set up a Givealittle page to help pay for the dogs' vet bills.
