Media reports say Australian surfer Mick Fanning's brother is believed to have died from a suspected drug overdose just hours before the champion competed in Hawaii.
Peter - Mick's 'hero' older brother - was reportedly found dead in a Tweed Heads home on Wednesday night.
A senior police officer confirmed to The Gold Coast Bulletin that a drug overdose was the likely cause of the 43-year-old's death.
Earlier on Thursday, Fanning took to social media to make a deeply personal and touching tribute to his brother - after competing in a third-round heat at the Pipeline Masters on Oahu's North Shore.
He took to Instagram and shared an old family photo of himself alongside his brother, which pictures them lined up with beaming smiles as they pose for the camera in their school uniforms.
'Like all my big brothers, Peter will always be a hero to me. I have so many great memories of the good times we have all spent together and they will be with me forever,' Fanning wrote to his 705,000 Instagram followers.
Mick Fanning, who survived a shark attack in South Africa in July, decided to keep competing at the Pipeline Masters in Hawaii to pursue his fourth world surfing title despite learning of the death of his brother.
Before entering the water for competition, Fanning was told his 43-year-old brother, Peter, had died back in Australia.
"It's kind of heavy to talk about right now," the 34-year-old Fanning said early in the day.
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He won his next two heats to reach the quarterfinals.
No cause of death was given for Peter Fanning.
Mick Fanning has endured a number of personal hardships throughout his career. In 1998, he delivered the news to his mother that another brother, Sean, had been killed in a car accident.
Today, Fanning posted on Instagram a childhood school photo of him and his three brothers, saying he and Peter had recently seen each other.
"He told me how proud he was of me and how much he loves watching me compete," Mick Fanning said in his post.
"Today was one of the most challenging days of my life, but I knew I could find the strength to take part in the final event of the season because that's what Pete would want."
A YouTube video of Fanning punching and fighting off a shark while competing at the J-Bay Open at Jeffreys Bay, South Africa, has been viewed more than 22 million times.
The death was confirmed by Fanning's Rip Curl team. "This is a sad and unfortunate incident and is a private matter for the family to deal with," a Rip Curl spokesperson told the ABC.
"We ask that the media respect their privacy. But we can confirm Mick's older brother Peter has sadly passed away. We will not be commenting further."
Earlier, the Seven Network reported Peter had been staying at Fanning's Queensland home following his recent divorce.
It's believed Peter, 43, had three children.
In August, Fanning's mother Elizabeth Osbourne told 60 Minutes of the pain of losing a child and how she feared it would happen again when Mick fought off the shark.
"I thought, the universe can't be this cruel," she said.
"And it also makes me think of the years we've had without Sean and how we really stuck together during that time and how beautiful it's been. "Only the one thing about our family now, especially me, is that I'm much more anxious."
- AAP and AP