The boy - described as angelic by a family friend - died in an accident at the Hilden Brewery involving a huge holding tank yesterday afternoon.
Oliver's father Owen, the brewery manager, was also injured in the accident.
He is the son of Seamus and Ann Scullion, who set up the Hilden Brewery operation in 1981.
The complex was sealed off by the emergency services in the aftermath of the tragedy.
As the police and Fire Service examined the site of the accident, guests were arriving at the brewery for a wedding party, oblivious to the family tragedy that had taken place just yards from their celebrations.
The Scullion family was too distraught to speak but wrote in a statement: "We are deeply upset by the death of a family member in an accident at the Hilden Brewery today.
"The family would like to request privacy at this very difficult time."
A NI Ambulance Service medical team had raced to the scene of the accident, but there was nothing they could do to save the little boy's life.
Last night, the Northern Ireland Fire and Rescue Service brought heavy lifting gear to the accident site to remove the fallen holding tank.
Local SDLP councillor Pat Catney, a close friend of the family who has known the little boy his whole life, said he was distraught.
His voice breaking with emotion, a shocked Mr Catney told the Belfast Telegraph: "The family are devastated. It's beyond grief itself.
"This is an indescribably tragic accident - it is difficult to find the words to convey just how painful this news is.
"Oliver was a force of nature - this little blond four-year-old wonder who enchanted everyone who met him.
"He was part of the life here at the brewery, and I know that the staff are also devastated at his death.
"All I can do now is help his mum, dad and siblings in their time of need. They will be forever in my thoughts and prayers."
Industry spokesman Colin Neill, the chief executive of Hospitality Ulster, offered his condolences and prayers to the ally bereaved family. "This is such a tragic loss," he said.
"The Scullion-Hanna family behind the Hilden Brewery are well-known and highly respected across the tight-knit hospitality sector.
"Our thoughts and prayers are with them at this sad time."
The Health And Safety Executive Northern Ireland (HSENI) is investigating the circumstances in which the accident took place.
A spokeswoman said: "The HSENI has been notified of the death of a young child at a commercial premises in the Lisburn area and is investigating the circumstances.
"We are unable to comment further at this stage except to offer our deepest sympathy to the family."
A PSNI spokesman said police had been in attendance at the sudden death of a child in commercial premises in the Grand Street area of Lisburn.
"The Health & Safety Executive has been informed," he added. "There are no further details at this time."
Hilden Brewery was founded in 1981 by Ann and Seamus Scullion, and is today run by their son Owen, Oliver's father. It is believed he is being treated in hospital for a broken leg.
Hilden is the oldest independent brewer in the island of Ireland. Last year the company announced plans to increase its brewing capacity from 7,000 litres to 14,000 litres after a rebrand and a rise in demand for its high-quality craft ales.
The Scullion family also owns the popular Molly's Yard restaurant near Queen's University.
"This is a deeply tragic event," said Alliance councillor Stephen Martin."The Scullions are well-respected members of our community and words cannot express the sadness we all feel on the passing of young Oliver.
"I was at the brewery a few weeks ago and, as always, it was clear the family are the driving force behind the success it has become. To lose a child is something no one should ever have to endure."