One of the residents, who would only be known at Brendon, was one of the first people to help.
"I just live up the road and heard a 'bang'. I just had a gut feeling 'this isn't going to be good'. I knew the sound had come from this intersection."
Brendon fled the house, grabbing a fire extinguisher from his car, and headed to crash.
"When I got here there's a lady in the passenger side [of the car] and it looked like she had already gone. I took her pulse, but there was nothing there," he said.
"Her husband, I'm guessing it was her husband, was there too. He seemed to have been knocked out for a bit."
Brendon said he used to be a volunteer firefighter.
"I looked around and there was a guy on the bank, looked like he was out cold."
Brendon said there were several off-duty doctors and nurses who had arrived at the scene and began taking care of the crash victims.
Other residents had taken up traffic management while waiting for emergency services to arrive.
Brendon said he's only lived in the area for two years but in that time there had been three serious crashes in the same spot.
"It's a crazy intersection," he said.
"It's just the traffic flow, it's gotten more and more since we've got here," Brendon said.
The section of SH2 where the crash happened is expected to remain closed for about another hour, and diversions are in place. Westbound traffic is being diverted down Te Puna Quarry Rd, with eastbound traffic down Snodgrass Rd.