Italian motorcycle rider Marco Simoncelli has died after a crash in the Malaysian MotoGP.
The 24-year-old's helmet was knocked off when he fell and was hit by Colin Edwards and Valentino Rossi as he slid across the track on his Honda.
The season's penultimate race was abandoned immediately after the collision just four minutes into the event, as Simoncelli lay motionless on the track.
Yamaha's Edwards also came off his bike but escaped serious injury, while Rossi was able to nurse his Ducati back to the pits.
Simoncelli lay stricken on the track before being taken to the circuit's medical centre where he was pronounced dead.
Casey Stoner, who won his second MotoGP title at his home Australian Grand Prix last week, said: "As soon as I saw the footage it just makes you sick inside.
"Whenever the helmet comes off that's not a good sign."