The three boys are from the area and the girl was visiting.
One of the first to the scene was a volunteer fireman who arrived to find the victim was his teenage nephew.
"It's the sort of thing you dread. You go to quite a few accidents and it's normally someone you don't know - but this was a bit close to home,'' he said.
The boy who died was the son and grandson of two other firemen at the Takapau Volunteer Fire Brigade station.
Fortunately, the boy's father and grandfather were working and unavailable to be called out to the crash, said the firefighter.
"That was a real blessing.''
Police are investigating the crash and were last night talking to the survivors and witnesses.