She said others in the truck initially thought Shane had survived the incident as he was "definitely alive for a while".
"One of them came into my house to ring the ambulance but he died before they got here."
The family member said the driver became distressed and angry after being told by St John staff that Shane had died.
She said the group had just left the house of the deceased and his brother and were heading to the Te Mahoe Village for a swim.
The woman comforted other family members who were waiting at the cordon before they were eventually given access to the scene.
Shane leaves his parents, Jury and Amiria Hohepa and brothers Hitaua, Dylan and Morehu.
One relative said Shane was due to start at Edgecumbe College after finishing at Edgecumbe Primary last year.
He was a "funny kid", who could be cheeky to fellow children, but was "just smart and cool". He was active and liked to play touch, rugby and ride horses, she said.
Another girl, who called the deceased and the driver her brother because they had grown up together, said she had been talking to them only hours before the accident.
"My poor, poor brothers," she repeated tearfully.
Members of the Tauranga police serious crash unit investigated the scene for three hours while cordons were set up at the intersections of Galatea Rd and McDonalds Rd and Galatea Rd and SH 2.
Senior Constable Stephen Allen of the Whakatane police said the 13-year-old was one of two people who were on the rear tray of a Mitsubishi utility when he fell on the road.
Mr Allen said police were calling for witnesses who saw the utility or its four occupants, two of whom were in the cab, travelling in the area before the accident.
The cordons remained in place until just before 5pm and were removed after the body had been taken away by an undertaker.
One woman said the fatality was the third in the same spot in the past five years.
"One involved a motorbike, the second involved alcohol and now this one today - and all of them in the same place," she said.
Just before 4pm tributes began to appear on the 13-year-old's Facebook page. One friend said "rest in paridise co" and another; "love yol stunnah, way too young ghee".
- Anyone with information for the police should ring Mr Allen on (07) 308 2308.