French gymnast Samir Ait Said suffered a shocking broken leg during the qualification rounds for the men's gymnastics at the Rio Olympic Park on Saturday.
The 26-year-old landed badly on the vault and his left leg folded beneath him, before swinging loosely below the knee as he fell to the floor.
After being attended by medics, Ait Said managed to raise one arm to acknowledge the ovation of the crowd before being taken to hospital.
French team leader Corrine Moustard-Callon confirmed Said had broken his leg, adding: "He is in the hospital with a doctor now.
"We don't know what happened, except that it was his tibia. We will do more exams to see if it just the bone.
"It is very difficult for the team. He was one of the friendliest on the team which is very difficult - he came to win a medal and gave everything 200 per cent."
One Twitter user said you could hear "the crack around the stadium".
This is not the first time an injury has dashed Mr Ait Said's Olympic dreams. The gymnast was forced to pull out of the 2012 Games because he fractured his leg in three places during the European Championships.
The injury came minutes after Germany's Andreas Toba hurt his knee during floor exercise. Toba abandoned his routine and was helped off by trainers but managed to compete on pommel horse before exiting to receive medical attention.
The U.S. men are leading halfway through the second subdivision thanks to a strong performance from four-time national champion Sam Mikulak. Great Britain, which took third at last year's world championships, is second. The top eight teams in qualifying will move on to Monday night's team final.
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