Sun climbed on the lane rope and waved four fingers on each hand in celebration. He pounded the water and was the last swimmer to leave the pool. Sun got out and thrust his arms in the air to screams and cheers from Chinese fans, who hung banners featuring his face from the stands.
"I was so thankful for my fans," Sun said. "I am aware that I have fans and also the haters in the venue, but I was just very satisfied to win."
Sun won his other 400 free titles in 2013, 2015 and 2017.
His presence at the world meet has drawn the ire of some swimmers, including Horton and American Lilly King. The Aussie is the only swimmer to beat Sun in the last eight years, taking gold in the 400 free at the Rio Olympics in 2016. That's when Horton called Sun a "drug cheat" for his three-month doping suspension in 2014.
Asked what his overriding emotion was, Horton replied: "Frustration. I think you know in what respect."
Olympic breaststroke champion King was critical of FINA, the sport's world governing body, for allowing Sun to compete at worlds.
"That's really sketchy and pretty insane," she said Friday.
Sun said, "I am aware of the rumours that have been going around, but I try to just concentrate on my swimming and I will keep trying to put a lot of effort in my swimming."
On the medals podium, Sun and Detti joined together on the top spot for photos but Horton didn't join them.
"I don't think I need to say anything," Horton said. "His actions and how it has been handled speaks louder than anything I could say."
Sun said he was aware Horton has a problem with him.
"Disrespecting me was OK, but disrespecting China was unfortunate," Sun said. "I feel sorry about that."
Sun is currently facing alleged doping rule violations that risk a ban from the 2020 Tokyo Olympics and he has requested a public trial at the Court of Arbitration for Sport in September to defend himself.
The World Anti-Doping Agency is challenging a decision by FINA, swimming's world governing body, merely to warn him over incidents during a doping control team's attempts to take blood and urine samples at his home in China last September, while allowing him to continue competing.
"I don't care about it," Detti said. "He won so today he was stronger than us. Next year I'll try to beat him."
In a massive shock Katie Ledecky didn't win the 400 freestyle final.
Ariarne Titmus of Australia chased down Ledecky over the last lap to win the final and deny the American star a record fourth straight title. It was Ledecky's first defeat in the event at a major international meet since 2013.
"This stings a little," Ledecky said. "It's not what I'm used to."
Titmus overcame a 0.62-second deficit going into the last lap and won by 1.21 seconds over Ledecky. The 18-year-old Aussie touched in 3 minutes, 58.76 seconds.
"I knew that I probably had that in me," Titmus said, "but, yeah, it's pretty surreal at the moment."
Ledecky finished in 3:59.97 — well off her world record of 3:56.46 set at the 2016 Rio de Janeiro Olympics.
"She ran me right down," the American said.
American Leah Smith took bronze in 4:01.29.
An admittedly nervous Ledecky had the slowest last lap of anyone in the eight-woman final. Titmus went 1.83 seconds faster over the last 50 meters.
"I made a move and then I came in at the last turn and felt like I could barely push off," Ledecky said. "My legs and arms just tightened up that last 50 and she took advantage of that."
Titmus led through the first 200 meters — dipping under world-record pace on the first lap — before Ledecky moved in front with 250 meters to go.
The American was still ahead turning for home. But Titmus pulled even midway through the last lap and surged to the wall first, becoming the first Aussie to win since Tracey Wickham in 1978.
"There was no pressure for me," Titmus said. "Katie's a true champion and I'm just happy that my swim was great today, but I'm sure she'll be back to race me again next year."
In the men's 4x100 freestyle relay, Nathan Adrian anchored the Americans to a victory seven months after announcing he had been diagnosed with testicular cancer.
Their time of 3:09.06 was a championship record, lowering the mark of 3:09.21 set by the U.S. in 2009 during the high-tech suit era.
The women's 4x100 free relay went to Australia in 3:30.21, also a championship record. The U.S. took silver and Canada earned bronze.
Adam Peaty of Britain became the first man to go under 57 seconds in the 100 breaststroke.
He won his semifinal heat in 56.88 seconds, bettering his old world record of 57.10 set last August in Glasgow, Scotland.
Peaty is seeking his third straight world title in the event. He also won the 100 breast at the Rio Olympics.
The final is Monday night.
