A pool of blood rapidly formed around him and he could be heard gargling and making a snoring noise before emergency services arrived, the judge said.
Mr Siaosi required emergency surgery to relieve the pressure on his brain after sustaining a variety of skull injuries.
Family and hospital staff nursed him back to health but two days before Christmas they were forced to relive the nightmare.
His stepmother Patricia Siaosi told the court a stroke left him fighting for his life yet again as he was placed back on life support.
"It was heartbreaking to see him worse off than when he first went into hospital," she said.
Since then, Mr Siaosi had been paralysed down his right side and his left eye was almost completely shut.
He has since been undergoing residential rehabilitation at a specialist medical unit in Ranui.
His mother Sandra Grey described the ordeal as her "worst nightmare".
"George not only lit up a room with his presence, he set it on fire," she said.
"We cannot forgive the person who has robbed us and George of so much."
Poai's lawyer Sam Galler stressed his client's remorse and put his actions down to "immature bravado".
Since the incident the defendant had completed alcohol and violence counselling, and Mr Galler said his prospects of rehabilitation were high.
Paoi's family were "disappointed" but continued to support him, he said, with an older brother even returning permanently from Australia to provide guidance.
The case gained headlines as police investigated fruitlessly for two weeks before the arrest of the teenager.
In a press conference at the end of September members of Mr Siaosi's family begged anyone with information to come forward.
Detective Inspector Gary Lendrum also voiced his frustration: "This macho bulls*** has to stop," he said.