Visiting Australian rider Sam Watson, a title contender, was first up and waved to the fans despite a suspected broken nose.
"I'm alright, I'm just p***ed off," he said.
But two more men required stretchers, one of whom was unconscious for some time, with all three being taken to Whanganui Hospital.
When events settled down in the early afternoon, there was some quality racing to watch in the signature Formula 1 event between guest England rider Richard Cooper, tackling the Whanganui streets sight-unseen, and Whakatane's Rees boys – fellow title contender Damon and older brother Mitch.
In the first race, Cooper came out strong, with the riders avoiding a close call on the front straight, as Mitch Rees and Taupo's Scotty Moir followed close behind.
The elder Rees brother was looking for inside lines but found the Englishman shutting the door, as Damon Rees worked his way up to third, and then finally on the ninth lap of ten Cooper left just a small opening and Mitch Rees was through it - lifting his wheel as he reached the checkered flag.
"It good drive off that [turn], and just had to squeeze on by," he said at the finishline, enjoying this year's series much more than 2018 when he was injured.
It became an identical podium in the second race, which unofficially should have given Cooper the title, as Mitch Rees again led the Englishman and his brother home.
The trio were having an absolute dogfight by the sixth lap of ten, and would go wheel-to-wheel for the remainder of the race, but Mitch Rees would not give Cooper the opening he had been afforded in Race 1, taking his second checkered flag and favouritism for the featured one-off Robert Holden Memorial.
Whanganui's Jayden Carrick gave a commendable effort in both F1 races, finishing sixth and seventh respectively.
However, in the Memorial, Cooper would turn the tables as for the second year in a row, there was a last-lap pass for the victory - denying Damon Rees yet again for the afternoon, this time after he had led all-but start to finish.
Mitch Rees had to step back to second fiddle this time, as his brother went out hard from the opening in the 26-rider field, taking the lead and sliding in and out to keep it, as again the top 3 riders were on the bubble of record lap times, being followed by local Richie Dibben, who had taken over the No2 Suzuki bike.
Cooper once again put on the pressure from second place, as a yellow flag came out on the last lap, and then in a surprise moment, the Englishman was able to sneak through as Damon Rees was slowed by lapped traffic, although the result was still unofficial at press time.
"Damo came out all guns blazing," Cooper explained after his victory burnout.
Incredibly, on a day when many riders had met untimely pavement, the Englishman had charged in the final part of the race despite losing his front break.
"It was a little bit nerve-wracking, in all honesty," he said.
"[When I passed Rees] I couldn't stop, even if I wanted to. Used the back markers to perfection.
"An awesome holiday and an even better Christmas."
For Dibben, it was a day of two halves as he completely cleaned up the two Supermoto races to sweep the series, yet his designs on higher honours in the Formula 2 class have been derailed this year after a tale of making the podium or being in crashes he didn't cause.
On his home track, Dibben had to settle for two runnerup placings in both F2 races, starting in the morning when he had been leading Hastings rider Adam Chambers up until the fourth lap.
Dibben still had a shot at victory coming to the white flag, but it was soon replaced by a red after a crash elsewhere on the track, and per the rules with over 65 per cent completed, the result was backdated to hand Chambers the victory.
"But lucky at the end. We'll take it," the Hawke's Bay man said.
In the second race, Dibben had to watch the back wheel of Auckland's Toby Summers from green flag to checkered flag, being just 0.003 to 0.009s behind him for the duration of the race.
Dibben tried gamely to put the pressure on, with Summers looking back early on to get a gauge on where his pursuer was, but the Aucklander held his nerve to get the win.
Another Whanganui rider Tarbon Walker showed great courage to come back from a spill earlier in the day to claim seventh.
Dibben took any frustrations he might have been feeling out on the Supermoto field – this division is his universe and the rest were just living in it.
In Race 1, Dibben passed for the lead early on the first lap and then was never headed, while at one point it appeared Whanganui riders might take all three podium spots, as Scott Dowman finished second, before New Plymouth's Mitch Rowe got up for third place.
Race 2 was absolute waxing, as Dibben had a quicker turnaround from his F2 race than earlier, and although this time it took three quarters of the first lap for the series winner to take the lead, the rest of the field had no answer as he powered away.
Dowman again climbed up to second, while the most intriguing battle between the chasing group.
Entering the last two laps, Dibben could have buttoned back, given he had the Memorial race upcoming, but instead he put on a show with blistering speed to take the chequered flag a full half-a-lap ahead of the rest.
"Nailed that one," Dibben said in the shed afterwards, although his disappointment that the F2 series had not gone as planned was clear.
"I think I would have ended up fourth [overall]. There's been a bit of carnage."
Dibben's thoughts now turned to the South Island in coming months.
"I'll do all the national stuff, finish up in April, then a bit of quiet time."
The other big success for Whanganui during the day was in sidechairs racing, as the brother-sister combination of Bryan Stent and Tracey Bryan were Classic winners in the Race 1A replay, which was just a four lap event after an earlier red flag.
Another red would be thrown on the last lap when the second and third bikes had a spin on the 'S' bend at the Suzuki Crossing, although Stent and Bryan were well on their way to victory at that point anyway.
There were a dozen locals in this Cemetery Circuit-only event, including several members of the Dowman family.
Bryan had also been a winner in the second F1-F2 Sidechairs race, as Race 1 was not replayed after the serious accident, when she rode sidechair for Tauranga rider Barry Smith.
The Whanganui Chronicle will have final results and series points placings in coming days.