Imogene Pyne, who was at the course for a 9-year-old's birthday party, saw Mr Brabet fall.
"Paramedics tried to resuscitate him for about 15 minutes, but he just didn't wake up. Then the ambulance arrived and they tried ... but they just couldn't wake him."
Ms Pyne, 30, said she heard somebody in the trees scream as Mr Brabet fell.
Paramedics tried to console his wife and asked her what happened, Ms Pyne said, but she was in a state of shock.
Other climbers were still in the trees with nowhere to go.
"There were two women behind me who were completely freaked out. They had nowhere else to look and watched the whole thing happen, this guy die in front of them, as we all did," she said.
"It was just horrific. Everyone was freaking out, they had a bird's-eye view of it all."
As soon as they saw the man fall, about 20m away, Ms Pyne and the parents of the birthday girl rushed to shield the eight children at the party from what had happened.
There were at least another 130 people at the scene, she said, most of them children.
"It seemed extremely busy and we got a tutorial from a very bored teenager on what the safety rules were. At one point, the father of the little girl whose birthday party it was had said to the manager, 'Hey, this place looks really over-crowded'," Ms Pyne said.
But another mother at the course, Jodi Stratful, said the pre-course safety briefing she and three 7-year-old girls with her received was good, and they were quickly evacuated from the course when the accident happened.
"The Tree Adventures staff handled this very well," she said.
Tree Adventures co-director Jimmy Moore did not return calls last night, but in a statement the company said safety was top priority and yesterday was no exception.
Tree Adventures insisted on a lengthy and detailed safety briefing prior to anyone using the course, as well as ongoing supervision from Tree Adventures staff throughout use of the courses, the statement said.
It was cooperating with the police and Department of Labour staff to determine exactly what happened.
The company extended its deepest condolences to the family members and friends.
A police statement said a doctor and an advanced paramedic were participants on the course and rushed to assist the man.
It is not known whether he had a safety harness on when he fell.
"Normal practice is two ropes at all times, so we can't quite understand how it happened," said Inspector Lance Gardiner.
Ms Pyne, too, was mystified about how the accident happened.
Tree Adventures uses harnesses and carabiners - metal clips that are meant to keep people attached to the safety system so if they slip, the harness catches them.
"I just have no idea how he managed to fall," she said. "I don't know what he'd done to be able to let that happen."
Police and health and safety investigators made a full examination of the scene.
The Herald understands the Ministry of Business, Innovation and Employment - which is now responsible for safety issues - has seized equipment the man was using.
It issued a notice closing Tree Adventures until further notice.
Were you there or do you know anyone involved? Please send your story, photos or video here.
This story corrects an earlier version that reported Mr Brabet's daughter was in the trees when he fell to his death.
- With Newstalk ZB
