Owen Kay's mum can't comprehend that her son could die at age 23.
"My brain is not letting me process this. I look to the hallway and can see him running down with his arms open to me and being an idiot," Sharon Kay said.
"I can't process a young boy celebrating his birthday, then not waking up."
Mr Kay, of Mount Elliot on the Central Coast, died on July 29, a day after his 23rd birthday.
He had been suffering from severe migraines for a few months.
He went to Gosford Hospital's emergency department a few times for treatment, but they didn't get to the root of the problem.
"A couple of times they sent him home, thinking he wanted painkillers. He felt like they were dismissing his concerns," Ms Kay said.
"He was going to pay for a private neurologist on the day he died. He had an appointment."
His death is unexplained for now, but the family suspects he died from an aneurysm or stroke.
His body remains with the coroner, who told the family his heart was fine. There was no foul play.
"He's had his autopsy. We're waiting for those results. We hope his body will be released this week once the cause of death is formally determined," Ms Kay said.
Mr Kay injured his finger in a workplace accident two years ago, for which he needed two surgeries. The last operation was about a month ago at Gosford Private Hospital.
"It's just speculation, but could he have got a blood clot from his operation? The only thing I know is he had bitten his tongue before he died. To me that's suggesting he had a seizure," Ms Kay said.
"When he had these migraines, he had lethargy, confusion and seizure-like symptoms. I told the doctors there's epilepsy in our family. They said if he had a seizure, it won't show up now because there's no brain activity."
The day before he died, he called his mum.
"He rang me up crying. He said mum, 'I can't handle the pain, these migraines are bad. I'm sick of feeling like this'. On his birthday he was a bit weird and groggy."
Ms Kay said her son would "act like he had Alzheimer's when he'd get these severe migraines".
"Sometimes he didn't know what he was saying. He'd ring me up, then ring me back to tell me the same thing. One day he rang me five times to tell me he loved me."
A GoFundMe has been set up for the family, titled "Funeral Fund for Owen Kay".
Family friend Monica Singh said "he was adventurous, fearless, cheeky and always looking for his next thrill".
"We all used to joke that if anything ever happened to Owen, it would be while doing something wild or daring because that was just who he was," she said.
"Yet behind that adventurous spirit was one of the kindest and most genuine people you could ever meet.
"Sharon wants his life to be remembered for the way he lived it, not for the way it ended. She wants people to remember the laughter, adventures, mischief, memories and the incredible young man he became."
Ms Kay, a mother of five, said her son was "my only boy, a sweetheart and a goofball".
"When he was younger, he would get his pocket money and bring me home a bunch of flowers," she said.
She said her son was "beyond a jokester".
"I always said don't put Owen near a set of wheels because he will end up in hospital," she said.
"Westmead Children's Hospital knew him by name through all the times he'd gone in as a trauma patient [he grew up in Sydney]. The nurses in the ward would say 'Owen you're back'.
"He was an adrenaline junkie, a motorbike rider and got into four-wheel-driving. He would skateboard. Anything with a set of wheels underneath, he'd do. He was so full of life."
