DAEGU - Usain Bolt was sensationally disqualified from the world 100m final on Sunday after a catastrophic false start, allowing fellow Jamaican Yohan Blake in to claim gold.
Bolt, the defending champion, Olympic gold medalist and world record holder, rocked off his blocks in horrendous fashion and knew immediately he had made the biggest error possible in the world of sprinting.
Under rules which state that athletes no longer have a second bite of the cherry in the event of one false start, the 25-year-old ripped off his singlet in disgust, and slowly retreated to the starting line, head in hands, to be steered off the track.
With the packed stadium abuzz in disbelief, it took several minutes for calm to return. Blake, a training partner of Bolt under coach Glen Mills, made the most of the clean restart to power through to win in 9.92sec in a muted atmosphere.
American Walter Dix, the Olympic bronze medalist, took silver (10.08sec) and 2003 world champion Kim Collins of St Kitts and Nevis claimed bronze at 0.01.
"I have nothing to say right now. I need some time," Bolt said.
Blake was left dumbstruck.
"I can't find words to explain it. Usain Bolt has been there for me. I feel like I want to cry," he said.
"I've been trained by one of the best coaches but I stayed cool and caught him (Collins). I felt I would win the race for Bolt."
Athletics' governing body, the IAAF, said it was "disappointed" by Bolt's disqualification, and issued a statement to explain the false start rule 162.7.
"The IAAF is, of course, disappointed that Usain Bolt false started in the final of the 100m," it said.
"It is important to remember that a sport's credibility depends on its rules and they must also be applied consistently and fairly for ALL athletes."
The current false start rule, applicable to all but combined events, has been in effect since January 1, 2010, "and all elite athletes have had the chance to adjust", the IAAF said.
Prior to the rule change, athletes had the right to make one false start and they were disqualified for a subsequent false start.
The omens had been good for Bolt, with three defending champions retaining their titles on the second day of competition.
American Brittney Reese won the women's long jump and teammate Trey Hardee the decathlon, while Russian Valeriy Borchin claimed a second consecutive world 20km race walking title.
There was also a first medal for China through Li Yanfeng in the women's discus, but heartbreak for Ethiopian distance running legend Kenenisa Bekele.
Bekele, bidding for a record fifth consecutive 10,000m title, was forced to pull out of the event he has never been beaten in with a groin/hip injury.
That left the door open for British favourite Mo Farah, but Bekele's teammates had other plans.
Ibrahim Jeilan produced an amazing home-stretch sprint to trump the Somalia-born Farah at the line of an enthralling race.
Farah had made a break shortly before the bell for the final lap, taking Jeilan and bronze medal winner Imane Merga with him.
It immediately became apparent that Merga was out of the running, but Jeilan remained as a contender.
Farah clung on until the final bend when Jeilan made his move, the two neck-and-neck before the Ethiopian sped away with a final burst of speed.
Jeilan finished the 25-lap race in 27min 13.81sec, just 0.26sec ahead of a despondent Farah while Merga clocked 27:19.14.
"I saw 100m to go," said Farah. "Unfortunately I dug in but my legs had no more.
"I thought I had the speed and he was finishing quicker and quicker - 53sec (for the final lap) wasn't quick enough. I didn't go too early, I was always going to go at 400-500m."
Hardee retained his decathlon title after amassing 8,607 points in the grueling 10-discipline event, with teammate Ashton Eaton producing the race of his life in the 1500m to take silver by just four points from Cuba's Leonel Suarez (8,501), who had been in second going into the final event.
Reese had sealed the first US gold of the worlds with a best leap of 6.82m in the women's long jump ahead of Russia's Olga Kucherenko (6.77m) and Latvia's Ineta Radevica (6.76).
Earlier in the day, Oscar Pistorius made history by becoming the first amputee athlete to compete in world championships history.
The South African, known as 'Blade Runner' because he runs with carbon fiber prosthetic running blades, came third in his 400m heat in 45.39sec, qualifying him for Monday's semi-final, with a dream final scheduled for Tuesday.