South Korea's Cha Dong-min took gold in the men's +80kg taekwondo, but former champion Angel Valodia Matos was banned for life for attacking the referee.
Cha beat Greece's Alexandros Nikolaidis in the final, while Kazakhstan's Arman Chilmanov and Nigeria's Chika Yagazie Chukwunerije took the bronze medals.
But the biggest drama of the day came with Matos' response after being disqualified against Chilmanov.
Matos shoved the referee and kicked him in the head in a furious reaction.
The Cuban took gold in the 2000 Olympics, but he did not take kindly to being disqualified halfway through the bout for taking too long to return to action after an injury.
Matos was leading 3-2, when he fell to the mat after being hit by his opponent.
Fighters have a maximum of one minute's break for injury, and the referee removed him from the competition as soon as the time elapsed.
Matos pushed and kicked the referee, drawing blood from the mouth, then attacked the Swedish judge before spitting on the floor and being escorted out of the arena.
Both Matos and his coach Leudis Gonzalez have been swiftly handed a lifetime ban from all World Taekwondo Federation (WTF) championships, subject to confirmation by the International Olympic Committee.
"This is an insult to the Olympic vision, an insult to the spirit of taekwondo and, in my opinion, an insult to mankind," said WTF secretary-general Yang Jin-suk.
Gonzalez was unapologetic for Matos' behaviour, saying the referee was "too strict".
Chilmanov expressed some sympathy with his opponent.
"To me it was obvious he was unable to continue," he said. "His toe on his left foot was broken."
But he added: "Rules are rules. I'm happy with my medal."
The shocking incident overshadowed the gold medal for Cha, South Korea's fourth taekwondo gold medal of the Games.
With the scores locked at 4-4, Cha unleashed a potent kick into Nikolaidis' chest, scoring a crucial point to seal victory.
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