A video of the incident, obtained by the Herald, shows a woman ploughing into the man on the footpath outside the superette. She then tries to drive over the man again, but a middle-aged man runs at the car to try to get her to stop.
The bystander chases the car as the woman drives off and two pedestrians go to the man's aid.
Kanj, who had recently completed an advanced St John Ambulance first aid course, said the man had severe cuts on his legs, a large bruise on his tailbone and was bleeding from the back of his head.
"I was shocked and I was shaking but I had to do something to help him.
"He was swearing a bit but we took him a cushion and another person got him a towel for his head and we tried to keep him comfortable."
The 44-year-old woman drove about 1km to Cobham Drive, then drove south - trailed by another motorist who saw the incident and had called police.
But she left the road, travelling at least 200m across parkland to the cliff.
Jahmaine Kati was swimming with his younger brother in the river when he heard the car rev shortly before it plunged over the bank.
"It didn't look like she was trying to stop," he said.
Mr Kati said the woman freed herself from the car as it sank.
He said police arrived quickly and officers jumped into the water. A passing kayaker helped the woman to shore.
Waikato police spokesman Andrew McAlley confirmed today the driver involved in the incident had been released from hospital yesterday.
"She's been sent for psychological evaluation."
The man involved was in a moderate condition at Waikato Hospital.
"Witness interviews will be taken during the week" and at this point, police could not make any further comment about possible charges, Mr McAlley said.
The police dive squad would also be recovering the vehicle involved in the incident this week.
- Additional reporting, APNZ
