Andrew Simpson, the British sailor who won gold at the 2008 Olympics, has died after a training accident in San Francisco.
The 36-year-old, who claimed the Star title in Beijing alongside his close friend Iain Percy, was part of a 11-man crew aboard Artemis Racing's AC72 catamaran which capsized in San Francisco Bay while training for the America's Cup.
Simpson, known by many as Bart, was trapped underneath the boat reportedly for as long as ten minutes and, despite attempts by doctors afloat and subsequently ashore, could not be revived.
"Our thoughts and prayers are with Bart Simpson's - Andrew Simpson's - family, his wife and kids" - Team Artemis ceo Paul Cayard
Artemis chief executive officer Paul Cayard said: "We obviously had a tragic day today on the bay and our thoughts and prayers are with Bart Simpson's - Andrew Simpson's - family, his wife and kids, and also with the rest of the team-mates.
"It is a shocking experience to go through and we have a lot to deal with in the next few days in terms of assuring everybody's wellbeing.
"The boat itself is under control, but it is certainly not the first of our concerns. We are focused on the people.
"That is what we are working with and on and we will give you more information when we are able to."
The cause of the accident was this morning not yet known.
San Francisco Fire Department spokeswoman Mindy Talmadge confirmed to Press Association Sport that Simpson was taken to St Francis Yacht Club on the shore where paramedics performed CPR, but was pronounced dead. She said another sailor suffered minor injuries.
Simpson represented Great Britain at two Olympic Games, sailing in the Star class alongside Percy.
The pair took gold at the Beijing 2008 Games and last year at the London Games were close to topping the podium once more, only to be bumped down to silver in the medal race.
Before last summer's Olympics, Simpson admitted that winning the America's Cup was his biggest goal.
He had hoped that dream would come true as strategist for challenger Artemis Racing, whose sailing team director and tactician is friend and long-time team-mate Percy.
The Royal Yachting Association released a statement early this morning after receiving the tragic news.
"We're devastated by the news from San Francisco today," RYA performance director John Derbyshire said.
"Andrew is someone I've worked closely with since the age of 16 - he was a great talent, and a key figure in our World Class Programme over many years culminating in his well-deserved Olympic success.
"He was a huge inspiration to others, both within the British Sailing Team and across the nation and our deepest sympathies go out to his family at this terrible time."
Tributes were paid from across the world of sailing and beyond.
Olympic silver medallist windsurfer Nick Dempsey said via his Twitter account "Going to miss you Bart", while Luke Patience, who took silver in the men's 470 class at London 2012, said: "Devastated. Bart, you are a true inspiration."
A statement from Ben Ainslie's Oracle team read: "Today is a sad day for all of us in the sailing community. Andrew Simpson was a great person, a terrific sailor, and a good friend to all of our team.
"Our thoughts are with his family and the entire Artemis team. He will be dearly missed."
Clive Woodward, British Olympic Association director of sport at London 2012, was another to pay tribute: "Totally shocked to hear Olympic star Andrew 'Bart' Simpson died after Swedish America's cup catamaran capsizes - thoughts with his family."