"They were encouraging the bikes, waving to the bikes ... I thought it was an accident waiting to happen," Mr Broadmore said.
"If they wanted to get involved in it, pull over and cheer from the roadside - what's a couple of minutes out of your time while the bikes go by and you can wave to them, instead of doing stupid antics?"
Mr Broadmore said he could not be certain if the same van was involved in the crash moments afterwards, but it was not far from the scene of the accident.
He said the group of about 100 motorcyclists decided to continue with the charity run after the crash because they were "there for the kids who go without".
"It's always bad when somebody gets hurt, but it's a charity run for people that miss out at Christmas."
He said a number of riders were upset and some chose not to continue with the run.
"It was quite a sickening feeling for a lot of the bike riders."
A 24-year-old Wanganui man, thought to have been driving the van, remains in a critical condition in Waikato Hospital, where he was flown from Taranaki Base Hospital.
The man, who was reportedly badly trapped in the vehicle, suffered multiple fractures and chest injuries.
The man's brother said on Facebook that he was "doing better", and was talking and asking how everyone was.
Three other men injured in the crash remain in Taranaki Base Hospital.
A hospital spokeswoman said two, aged 22 and 27, were in a comfortable condition, and a 62-year-old was described as stable.
Meanwhile, a 42-year-old man, who was also injured in the collision, had been transferred to Middlemore Hospital in Auckland in a serious but stable condition.
Police said it was too early to say if charges would be laid.
The Taranaki Motorcycle Club, of which Mr McKay was a member, held a minute's silence to remember the motorbike enthusiast today.
Club vice president Mitch Rowe said Mr McKay was a passionate member of the club.
"He greatly supported our motorcycle events. He'll be missed in our club."
Mr Rowe said Mr McKay was a "great" person with a generous spirit, always wanting to help others.
A relative of Mr Reardon, who did not want to be named, said he was "nice and caring person".
The men's deaths were among six fatalities, including four motorcyclists, and more than a dozen injuries on North Island roads this weekend.
A total of 267 people had died on the roads in the year to Friday - up on 250 by the same Friday last year - with the weekend fatalities bringing the total road toll to 273 this year.
Yesterday, two other motorcyclists and two people in cars were killed in separate accidents and 10 others were injured in crashes.
Among those injured were three males, aged between 16 and 22 in a crash on State Highway 2 north of Wairoa about 6.30am today.
One patient with multiple serious injuries was taken to Hawkes Bay Hospital by the Lowe Corporation Rescue Helicopter.
The crew then flew to Wairoa Hospital to pick up a second seriously injured man and another man with a shoulder injury, who was taken to Wairoa by ambulance.
Both were flown to Hawkes Bay Hospital.
A third seriously injured man with head injuries was airlifted to Hawkes Bay Hospital by the Gisborne Rescue Helicopter.
