Sun Yang's shock last-minute withdrawal from Sunday's 1500 metres freestyle final with a heart problem has cast a shadow over the last night of the world swimming championships in Russia.
China's world record-holder and Olympic champion confirmed his 11th-hour decision to quit was made after having chest pains during the warm-up as his sudden withdrawal caught FINA officials by surprise.
It meant the 400 and 800m world champion's lane was empty for the final as Italy's Gregorio Paltrinieri won the 1500m world title in his absence.
The 23-year-old Sun said he will seek medical advice after flying back to China on Monday and confirmed this was the first time he has been affected in competition.
"After the 800m competition, I didn't feel well in my heart. I felt uncomfortable in the warm-up tonight so I had to give up the idea of competing," said Sun.
The Chinese giant courted controversy in 2014 after it emerged he had served a three-month doping ban for taking a banned stimulant.
Trimetazidine was in a prescription drug he sometimes took for heart palpitations.
Sun gave a 'no comment' to numerous reports that he was involved in a physical altercation with a Brazilian swimmer Larissa Oliveira in the warmup pool on Sunday morning.
Several swimmers have confirmed there was a heated exchange and reports in Brazil's media say Sun attacked Oliveira with an elbow while Brazilian officials have made a formal complaint to FINA.
Earlier, Australia's Bronte Campbell completed the freestyle sprint double as the 100m champion added the 50m crown.
It's fantastic, I can't believe it," said Campbell, who finishes with three golds and a bronze from the 4x100m medley relay after her 50m triumph.
"I really didn't expect to win. Anyone in the final could have won this race."
The 21-year-old clocked 24.12 seconds to win gold with previous champion Ranomi Kromowidjojo of the Netherlands taking silver at 0.10sec back as Sweden's Sarah Sjostrom earned bronze at 0.19.
Campbell's elder sister Cate missed out on a medal as she finished fourth at 0.24 in a blanket finish.
Sjostrom was happy with bronze as she leaves Kazan with five medals after her 50 and 100m butterfly golds, as well as silvers in the 100m freestyle and 4x100m medley relay.
The 21-year-old also broke the 100m fly world record twice.
Hungary's 'Iron Lady' Katinka Hosszu lived up to her nickname by completing the individual medley double in the 400m final having also retained her 200m title earlier in the week.
Hosszu touched the wall at 4min 30.29sec - just under two seconds short of Ye Shiwen's world record she had been chasing - to leave her with two golds from Kazan and a 200m backstroke bronze.
In the men's 400m IM final, Japan's Daiya Seto retained his title and admitted his failure to qualify from the 200m semi-finals had given him all the motivation he needed.
There was a shock in the women's 50m breaststroke final as Sweden's Jennie Johansson snatched gold at 30.05secs in a blanket finish to claim her first major title.
Jamaica's Alia Atkinson claimed silver at just 0.06sec back while Russia's reigning champion Yuliya Efimova took the bronze at 0.08.
Australia's Mitchell Larkin missed out on a backstroke treble after claiming the 100 and 200m world titles earlier in the week.
He finished fifth in the 50m final as France's Camille Lacourt defended his sprint title.
In the 4x100m medley relays, China's women took gold ahead of Sweden and Australia, while the USA claimed gold in the men's race ahead of Australia and France.
For the seventh consecutive championships, the USA finished top of the table in the swimming events with 23 medals, while Australia took second with 16, China third with 13 and Britain fourth with nine.