Ms Tohi had filmed the match, and in the middle of packing up and gathering children Julius, 7, and Leila, 4, to head home, she saw her husband-to-be collapse.
"I saw him drop down on one knee. I didn't think anything of it at first. The next time I saw him, he was on the ground. I initially thought it was his knee, because he'd had an issue with it a couple of games back.
"We went over. He was just lying there. I've never seen him like that. He sounded like he was asleep."
Mr Halaifonua was diagnosed with a brain bleed, and after a three-hour emergency operation, he was placed in an induced coma.
He died three days later.
He passed away naturally, Ms Tohi said. "I don't think I would have been able to make the decision (to turn life support off). It was very peaceful and quite nice because everyone was there, even his team and his coaches. I'd like to go like that, surrounded by everyone I love."
Ms Tohi is not angry about what has happened and does not believe anything could have been done to prevent Mr Halaifonua's death.
"I got asked: 'Do you blame rugby?' How can I? At least he passed away doing something he loved to do. I'll never understand it, but my faith is strong and it's not a time to be angry."
The North Harbour Rugby Union is investigating Mr Halaifonua's death. But Ms Tohi is adamant there is no way it could have been predicted or prevented. She does not want his club to be blamed or scrutinised.
"It's just one of those things that happens. It's rugby. Unless you're covered in bubble wrap, it can happen," she said.
Ms Tohi's face lights up when she remembers her man. He proposed last year and they planned to marry this year but hadn't set a date.
"This year would have been our 10th anniversary," she said. "He was everything ... He had a big personality and a great sense of humour - even if I didn't always get it. He had a big heart, he was just perfect. I literally cannot find words that are good enough to describe Willie. He was above amazing.
"He was devoted to us and the family, he was a very good dad. Willie was the type of person who would put everybody else before himself."
Since he died, Ms Tohi has spent as much time as possible with his family, and away from their own home.
"It's the silence at home I can't stand. I'm taking it one day at a time. I have to be strong for our kids. Everyone says, 'You're so strong', but I don't have a choice. I can't break down in front of my kids, because if I do, they will. Willie wouldn't want me to sit there and cry over him. He'd want me to look after our babies, so that's what I am doing."
Family message
A message from Turea, Julius and Leila:
"We would like to thank the Takapuna Rugby Club, New Zealand Rugby Foundation, the NZ Customs Service (Turea's employer) and all of our friends and family for their support and love. It's been so overwhelming. Thanks also to everyone else who supported and helped Willie and our family."
The New Zealand Rugby Foundation has set up the Willie Halaifonua Trust Fund. Donations can be made to BNZ A/c 0201920514849097.
