It was understood he had permission to be riding the bike at the time, Mr Rackliff said.
Serious crash investigators completed a thorough scene examination and police have notified the coroner.
"Victim Support and police are currently providing support to the family at this difficult time."
Police said the incident occurred about 1km from the farm gate, on the property about 13km south of Featherston.
An ambulance and hearse were seen leaving the farm soon after midday yesterday.
Police vehicles were also coming and going during the day, along with others arriving to provide support to the sharemilking family.
A tow truck arrived in the early afternoon and left a short time later loaded with a quad bike.
Clare Crawford, principal of Kahutara School where Shane was a pupil, visited the family yesterday afternoon.
Mrs Crawford said the crash was every parent's nightmare.
"At the end of every term time I say to the kids, 'Have a safe and restful holiday and we'll look forward to seeing you all next term'," Mrs Crawford said.
"You never dream that you won't be seeing one of them."
Mrs Crawford said Shane was a valued team member of Kahutara School and "a big part of the school environment", being involved in all aspects of school life including sport and kapa haka.
"Kahutara pupils, staff and families are grieving the loss of a well-liked student," Mrs Crawford said.
"Shane was a positive, helpful member of his class."
A Year 6 pupil, Shane was part of the 30-strong senior class, which also includes Years 7 and 8, at a school of 100 children.
"We are a small country school and a very close community, and Shane's loss will be felt throughout," Mrs Crawford said.
Neighbour John Pearce said the incident was "absolutely horrifying and tragic", but he did not want to see any "recriminations about rural children".
"These things happen in all walks of life," Mr Pearce said.
"Many years ago people rode horses, and people fell off horses and died as well."
