"They were here seeing grandad at grandad's place...
"The kids were playing hide-and-go-seek. It is a big house they were in and it has an internal lift."
The sprawling house has three levels, and the lift is a 1.5m by 1m platform that moves between each, with a doorway and window on each level.
The doorway and window -- a small glass panel -- are on opposite sides of the lift.
The builder said the boy went missing during the game.
"He was missing for about half an hour. We couldn't find him and then [the man] who owns the house opened the lift door and there he was."
The boy was lying on the floor of the lift and was unresponsive, with extensive head injuries.
"He would have been in the lift a little while before we got to him, the poor little guy.
"We spent about 30 minutes trying to revive him before the fire brigade arrived and then they took over. I was working on him for a while and I thought I had him.
"They worked on him for a good two hours trying to get him back."
The Manly Fire Station in Whangaparaoa was called to the incident, but a spokesman would not comment on the service's role there.
St John also rushed to the scene but said the boy was deceased when paramedics arrived at the address. The Auckland Westpac Rescue Helicopter was also notified, but stood down soon after.
The builder said the accident was "shocking" and he could not stop thinking about what had occurred.
"He must have been lying on the floor, because if he was standing it couldn't have happened, and he must have been lying there hiding from his sister and stuck his head out to look out the window at the wrong time.
"That's the only way I can think that it would have happened because those lifts are safety conscious things."