He told Fairfax Media the car was doing about 120kmh when it came off the road.
"I watched it shoot through the forecourt still doing that kind of speed, shoot straight through the pumps and out the other side, hit the bank and barrel roll just like a fighter plane."
Mr Davey said the children looked like they could be moved, but the adults were "obviously in a bad way".
''We got the kids out through the tailgate, we managed to get them out from where they were buried underneath mum, who pretty much lost her face, poor woman.
The remaining occupants were cut free by the Fire Service.
The passengers were airlifted to Wellington Hospital by Life Flight, in critical and serious conditions.
Sergeant Moody said the cause of the crash is being investigated and anyone who saw
what the accident should contact Wellington Police on 04 381 2000.