"We don't want anyone else to die," national road policing manager Superintendent Steve Greally said.
The death brought the toll up to five - two higher than last year's Labour Weekend toll.
Adam Moss, 15, was doing work experience at the mini golf course when he heard the crash this morning.
"I heard some skidding along the road, then a big bang when the motorcycle hit the car. Then I heard some people screaming."
The young man rushed to the scene of the accident, to find a motorcyclist had hit the driver's door of a white station wagon as the car turned into the mini golf course.
"He was in a bad way. It looked like his jaw might have been broken and his face was quite stuffed up."
Mr Moss was joined by a doctor who had been at the mini golf course.
"I went and got a first aid kit and then he asked for a tube because the motorcyclist wasn't breathing."
Mr Moss rushed back to the golf course, knowing exactly where to find a piece of tube, and when he returned within a minute, it was stuck down the motorcyclist's throat to clear his airway.
The motorcyclist was taken to Wellington Hospital in a critical condition. He later died.
Senior Sergeant Braydon Lenihan said the preliminary investigation indicated that speed was a factor in the collision, but the serious crash unit would determine its exact cause.
The death comes after two fatal crashes in Southland this morning.
In the first incident, an Australian woman was knocked down and killed while walking on State Highway 1 near Bluff about 1am. The death was being treated as a homicide investigation until foul play could be ruled out, police said.
Police have called for sightings of anyone walking on the highway from 9pm yesterday until 1am today, including a woman wearing a blue jacket and pink shoes.
Later, a woman's charcoal-coloured Nissan two-door car tore through three sets of traffic lights before ploughing into the Farmers store at the corner of Yarrow St and Dee St in Invercargill about 7.15am.
Officers were investigating whether she suffered a medical event prior to the crash.
On Sunday, a male pedestrian died after being struck by two trucks on SH29 in Waikato about 2.30am.
Later that morning, a 21-year-old Puketutu man was killed when the motorbike he was riding crashed at the intersection of Hutchinson and Morrinsville-Walton roads about 6am.
Mr Greally said the two Southland deaths would not count towards the road toll if foul play or a medical event were found to be the causes.
The 2015 road toll already exceeds last year's by at least 29, with the number of deaths on New Zealand's roads sitting at around 233.
Mr Greally said the weekend road toll was "disappointing".
"It will take a little time until we can understand exactly what's occurred, but suffice to say it's tragic that we've had ... people lose their lives.
Despite the deaths, Mr Greally said "by and large" motorists were observing the rules this Labour Weekend.
"I think the behaviours, by and large, are actually not too bad, which is a good thing."
However, Mr Greally warned that "a lot of people" would be travelling back home today on the country's main arterial routes, particularly into Wellington and Auckland.
That sort of congestion would "breed frustration", he said, "and when people are frustrated their potential to make a poor decision, take a risk, is a lot higher".
"And of course we all know what happens then - innocent people are placed at risk.
"We don't want anyone else to die, we don't want anyone else to end up in a wheelchair for the rest of their lives this weekend, or any day of the year."
Police would be "highly visible" along the main roads into the capital and Auckland this evening, he said, and officers wouldn't hesitate to pull people over if they were not abiding the road rules.
A reduced 4km/h speed threshold was also in place.
He also called on motorists to take responsibility for their own driving.
FATAL CRASHES
• Monday - A woman died after a car ploughed into the Farmers store at the corner of Yarrow St and Dee St in Invercargill about 7.15am.
- A woman pedestrian died after she was hit by a vehicle on State Highway 1 near Bluff about 1am.
- A motorcyclist died in a fatal crash on a 70km/h stretch of Happy Valley Rd in Wellington.
• Sunday - A male pedestrian died after being struck by two heavy trucks on State Highway 39 in Pirongia, Waikato, about 2.30am.
• Saturday - A 21-year-old Puketutu man was killed when the motorbike he was riding crashed at the intersection of Hutchinson and Morrinsville-Walton roads about 6am.
INJURY CRASHES
• Monday - A man escaped with minor injuries after his car flipped on its side on State Highway 1, about 3km north of Maroa Rd near Oruanui in the Bay of Plenty.
- A motorcyclist suffered leg injuries in a collision with a car on Waiteitei Rd, Te Arai, north of Auckland this afternoon.
- A 51-year-old man suffered minor injuries after being trapped in his car after it left the road and crashed into vegetation on State Highway 1 near the Maroa Rd intersection between Rotorua and Taupo around 10.35am.
• Sunday - Seven people were injured - one seriously - in a three-car crash State Highway 30 near Rotoiti, about 25km north-east of Rotorua about 9.30pm that resulted in one of the cars being ripped in half. A 20-year-old local man was taken to hospital with suspected spinal injuries.
- Three people were lucky to escape with minor injuries after a sports car lost control and hit a bank shortly after overtaking a bus on the Whangamoa Saddle, near Nelson. The car then careered across the road and over the opposite bank, before hitting trees.
- Shortly afterwards, a motorbike crashed into vehicles which had pulled over to help the occupants of the sports car. The rider was thrown from the bike, and taken to hospital with a suspected broken leg.
- A male driver was in serious condition after losing control of his car and crashing into a power pole on Moorhouse Ave in Christchurch about 3am. The driver and two male passengers - all in their late teens or early 20s - were taken to Christchurch hospital.
• Saturday - A 19-year-old Tauranga man was left fighting for his life after being hit by a ute in a suspected hit and run incident in Te Tumu Rd, Paengaroa, at about 9pm.
• Friday - A 41-year-old man was taken to hospital in a serious condition suffering a head injury after crashing through a fence, down a bank and into a house at Hampton Terrace, in Parkvale, Tauranga, at 11.20pm.
