Norwegian Olympic star Alexander Dale Oen has been found dead at a training camp in Arizona.
The 26 year-old is thought to have suffered a cardiac arrest in his room, after taking part in a light training session on Monday.
Dale Oen was crowned 100m breaststroke world champion during the 2011 world championships in Shanghai, and was considered a huge medal hope for the 2012 Olympic Games.
His team mates and coaches were devastated after being informed of the tragic news, with Petter Loevberg, Norway's swimming coach commenting: "We’re all in shock. This is an out-of-the-body experience for the whole team over here.
"Our thoughts go out to his family who have lost Alexander too early. Words cannot describe the grief they must feel.
"For us here in Flagstaff it is important now that we stand together and take care of each other. It is an unreal situation and we have some tough days ahead."
Oen had been aiming to build on his Olympic silver medal from the 2008 games in Beijing, which was consequently Norway's first ever Olympic swimming medal.
His world championship gold last year came days after Anders Breivik's massacre of 77 people, leading Oen to dedicate his victory to the people of Norway. "We need to stay united" he said at the time. "Everyone back home now is of course paralysed with what happened but it was important for me to symbolise that even though I’m here in China, I’m able to feel the same emotions."