"He's just collapsed onto the ropes."
Knight was due to marry Michelle Burke in three weeks, Fairfax reported.
Burke was at the event last night and was listed as a competitor. She tried to administer CPR to Knight after he collapsed, witnesses told Fairfax.
It is unknown what caused Knight's death or how long he had been fighting before collapsing in the ring. Police say the boxer's death will be referred on to the coroner.
Early this morning the Facebook page for Nabby's Boxing Gym, which ran the event, posted about how its boxing whanau were "devastated."
"This amazing family have been part of our whanau for two years, three family members fought tonight and they loved the sport," the post read.
"You trained hard Nev, you earned your name the 'Terminator'. RIP."
Tributes have been flowing in for Knight on Facebook this morning, with Alfie Webb saying the death was "a truly devastating blow to Nev's immediate family and also the Nabby's Boxing family."
Another post read: "You were a well respected man and will definitely be missed. So sad."
Knight was listed to fight Nick Trott, a former DJ for The Rock, who told Fairfax Media last night he was "numbed" after the incident.
"I'd like to send my prayers to Nev's family. I know them, I trained with Mitch, his fiancée. I weighed in with Nev this morning. We both did our medicals. It's numbing," said Trott, who fought fellow radio host Grant Kereama in the 2003 Fight for Life.
Duco boxing promoter Dean Lonergan was not at the Hamilton event, but said Knight's death was "a bloody tragedy".
Although boxers often got injured during fights, it was unusual for them to die in the ring.
Lonergan was not aware of any other deaths like this in New Zealand, but mentioned an incident in Sydney last September when David Browne Junior, 28, was knocked unconscious during a boxing title fight at the Ingleburn RSL club and later died in hospital.
"This is a bloody tragedy. We never want to see this stuff happen," Lonergan said.
It was likely Knight and the other boxers were medically assessed before entering the ring, but Lonergan said he did not know what health and safety procedures Nabby's Boxing Gym had in place for the event.
Hamilton boxing coach Merrill Purcell said Knight was a good fighter and had fought two of his boxers in the past few years including the Tongan Bear last year.
"I knew Neville. He was one of the nicest guys around... He could handle himself. He was pretty good. He wasn't sickly or didn't seem to have any medical problems. He was good."
Purcell, who was attending another fight in Hamilton last night, said the news had come as a shock.
"He's a corporate boxer. A corporate boxer is one that hardly fought. Generally a corporate boxer is one that trains for six weeks/two months. They usually just have one fight and that's all, but some of them get to like it."
Purcell had seen him fight three times and recalled training Knight's son at the Nawton Boxing Club last year. "He was ok, he was a very strong man Nev. It's kind of a surprise.
"I think he went there (Nabby's Gym) for the exercise and because he was so popular he got in the ring. Everyone he was around was a fighter - I had most of his workers at my gym."
Purcell said it was compulsory for boxers to provide medical certificates from their own doctors and also have a medical from a doctor before a fight weigh-in. He said it was not uncommon for people to get hurt, but he couldn't recall anyone dying in the ring.
Police confirmed the man "collapsed" at the fundraising event held at the gym, which is based at Te Rapa Racecourse.
"It was a charity fight night, our understanding is the fighter collapsed in the ring," a police spokeswoman said.
"A doctor was on site and an ambulance attended, but they were unable to revive the boxer."
A witness told Fairfax she saw the man hit the ropes, then the ground.
"I don't know if he was hit - I just saw him hit the ground. The ambulance staff have been working on him for quite a while," she said.
"We were told to leave the hall about 9pm while the ambulance staff were still working on him. They are trying to resuscitate him. I think he's dead."
The witness told Fairfax there was no defibrillator at the venue.
"While they were resuscitating him a lady came on the loud speaker asking us to pray for him, then started crying," she said.
"Then an official came on the loud speaker asking us all to leave out of respect. And there would be no more fights tonight."
Police said the man's family and friends were at the venue during the incident.
Last night's event was dubbed "Young Guns 2".
It appears many of the fighters were inexperienced. In the run-up to the event, the Facebook page for Nabby's Boxing Gym complemented the skills of a boxer with only three prior bouts under his belt.
Just hours before the event, another post encouraged all participants to enjoy their charity fights, saying "Only hours away until kickoff big ups to everyone from our Foodies Fight Night crew that has been training for the last 10 weeks it has been amazing to see how far you guys have come, win or lose you have done yourself proud and myself Ike and Scotty. Get out there and enjoy yourself tonight [sic]."
