While it was not clear what sparked the burst of violence, he saw the two men holding down the driver of the black car.
At another point, he also saw five people — the two men from the silver car, the driver and his female passenger, along with another woman who was possibly a passerby — who were involved in the melee.
The women appeared to be trying to get the men off, he said.
The crash had left the witness feeling “pretty shocked”.
Police had responded very fast, he said.
Severe damage could be seen to the side of the Subaru, and also to the front of the black car which had rolled after the crash and come to rest at the bottom of the hill.
A Hato Hone St John spokesman said it was called to the incident at 2.37pm.
Two ambulances were sent along with a rapid response vehicle.
One patient was treated at the scene for moderate injuries, while another person was taken to Dunedin Hospital with serious injuries.
A police spokeswoman confirmed police were investigating after responding to reports of a crash followed by an assault.
Officers remained at the scene and police were aware of one person being injured, the spokeswoman said.
Following the crash, a man could be seen being helped into an ambulance by police.
Across the road, officers were speaking to another man who had been placed in handcuffs.
