The accident occurred sometime after 2am when the people at the property had gone to bed.
Senior Sergeant Ian Row, of Northland police, said it was a ''very, very horrifically unfortunate accident''.
''I don't usually use the word accident but this one was. For some reason the handbrake seems to have failed. The vehicle has then rolled downhill and struck a tent.''
The vehicle had been examined to determine whether the handbrake was faulty.
The police investigation was complete and it was now a matter for the Coroner, Row said.
Police enquiries are continuing.
The death was the fourth accidental death over the holiday period in Northland.
A woman, believed to be local and in her 60s, died when the boat she and two other people were in flipped in surf on East Beach, between Houhora and Rangaunu Harbour, on Friday morning.
A local fisherman said an off-duty Coastguard volunteer spent 30 minutes trying to save her life. Police have yet to release the woman's name.
And on Christmas Day 44-year-old Hanbo Bao (known as Campbell), from Albany, died whilst catching crabs at Uretiti Beach.
The second Christmas Day drowning involved a snorkeller at Kai Iwi Lakes about 3pm. The name of the snorkeller has yet to be released.
The water deaths prompted a plea for people to take more care on the water and observe the basic rules.
Surf Life Saving northern region chief executive Matt Williams advised people to be ready and prepared when visiting and enjoying the beach this summer.
He said the sad events of the past few days should prompt the public to be aware of beach safety messages.