The third patient - a Tauranga woman - was in a moderate condition in a ward.
An emergency department nurse, who spoke to the Bay of Plenty Times on the condition she was not named, said she did not see the crash but had been heading home at the time and pulled over to help.
The man driving the car, which ended up in a water-saturated bank on the left side of the road, was in an extremely bad way, the nurse said.
"He was unconscious, his lips were blue and the steering wheel was pressed up against his chest while the whole right side of the dashboard was across his legs," she said. He also had a large wound on his head.
"I held the man's head up, cleared his airways and tried to keep him stable while we waited for the emergency services to arrive. It seemed to take an awfully long time. The man was unconscious for about 10-15 minutes."
The nurse said once he regained consciousness he was "extremely distressed" and clearly in a great deal of pain.
She said she tried to keep him calm, while the firefighters cut him free from the car.
The man, who appeared to be in his mid 60s told her he had been heading back to Tauranga from Katikati.
"I could hear the woman in the white van which ended up on a verge on the other side of the road was screaming. I had no idea there was a third person injured," she said.
The Serious Crash Unit were still investigating the crash, and police said they were keen to speak to anyone who witnessed it.
Call Tauranga Police on 07 5774300 or provide the information anonymously via the Crimestoppers line on 0800 555 111.