"I was standing at the back end and I forced it up and I told him to get out as fast as he could."
Mr Hepi, 18, was taken to hospital.
The drama happened yesterday about 9.30am at the Bellevue, property where the two men live.
Their flatmate Sativa Dagg said Mr Hepi had reached in to get something out of the car, which was unused and unregistered, and "must have accidentally knocked" the gearbox.
"It was purely accidental. There was no key in the ignition so he must have knocked it," she said.
"He closed the door and it sat there for a while, then it started moving."
Mr Tawera woke up to the sound of Miss Dagg screaming and rushed outside to see the runaway car career down the steep driveway and run over his cousin.
"I ran down the driveway and saw my cousin stuck under the car, so I stood at the back end and lifted it up."
Miss Dagg said Mr Hepi stood up for a short while but lay down on the ground and waited for an ambulance to arrive.
Mr Hepi said from Tauranga Hospital, where he was being observed yesterday afternoon, that he did not remember much other than looking over his shoulder and seeing the car "seconds away from my face".
"Then I must have blacked out for a bit but I remember [underneath the car and] my hands were right up at my chest, pushed up against the bottom of the car."
"I remember [Mosh] telling me to get out from underneath but I was already thinking that so I rolled out on to the neighbour's lawn."
Miss Dagg said Mr Tawera was a "hero".
Mr Tawera said a surge of adrenaline gave him the extra strength to lift the car.
But he didn't see himself as a hero.
"Nah, it's just another day in Tauranga."