Teenager Pan secured Olympic gold on Wednesday with a stunning 46.40 seconds, shattering his own world record of 46.80 set in February, finishing a body length ahead. The day before, Pan had barely made it into the semi-finals with a time of 48.40, two seconds slower.

Hawke, an Olympic sprint freestyler who later coached Brazil's Cesar Cielo, the first man to break 47 seconds, expressed skepticism about Pan's world record, calling it "not humanly possible."

"Listen, I'm just going to be honest. I am angry at that swim, I'm angry for a number of reasons," he said in an Instagram video. "My friends are the fastest swimmers in history – from Rowdy Gaines to Alex Popov to Gary Hall Jr, Anthony Irvin, all the way up to King Kyle Chalmers. I know these people intimately, I've studied them for 30 years. I've studied this sport. I've studied speed. I understand it. I'm an expert in it, that's what I do, okay," added Hawke, now a US citizen.

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"That's not real, you don't beat that field, Kyle Chalmers, David Popovici, Jack Alexy, you don't beat those guys by one full body length in 100 freestyle. That's not humanly possible, okay."

Pan's victory comes amid a doping controversy surrounding the Chinese swim team, leading US authorities to accuse the anti-doping governing body WADA of a cover-up. The New York Times reported in April that 23 Chinese swimmers tested positive for the banned substance trimetazidine (TMZ) at a domestic competition in late 2020 and early 2021 before the Tokyo Olympics.

Pan was not among the 23 swimmers mentioned in the report. Chinese authorities claimed the positive tests were due to food contamination, an explanation accepted by WADA. Chinese swimmers have been extensively tested before the Olympics. "Last year I received 29 tests, and it has never been positive," Pan said after his win, which he described as "a perfect performance." "I was tested after the race and we will see the result."

Australian veteran Chalmers, who won 100m gold in Rio and silver in Tokyo, accepted Pan's performance without question. When asked by Australian media if he believed the record was clean, he replied: "Yeah."

"I do everything I possibly can to win the race, and I trust that everyone's doing the same as I am and staying true to the integrity of sport. I trust it, I trust that he's done everything he possibly can to be there and he deserves that gold medal. 

"I did everything I possibly could to challenge for that gold medal and be on the top of podium. I'm silver and I'm just as happy with that."