"Unfortunately the driver, who did the right thing, suffered more serious injuries and he was taken to Waikato Hospital by ambulance for treatment.
"Such behaviour cannot and will not be tolerated. In such situations a driver is obliged to stop and ascertain any injuries.
"If people known to the victims then take matters into their hands then they will be held to account.
"It is the police's role to investigate and hold people to account, not emotional bystanders," Mr Nicholls said.
Police were continuing to investigate the incident.
The incident was the second in Hamilton yesterday which involved a pedestrian being struck down by a car.
"Earlier, shortly before 5pm, a 13-year-old girl went to cross a street in the CBD against a red pedestrian signal.
"Changing her mind she has then turned back but been struck by a slow moving car and was taken to Waikato Hospital with minor injuries.
"In both these cases the initial victims were lucky in that speed was not a factor."
Last year five pedestrians died on Waikato roads.