Heartbroken tributes poured in from the 24-year-old's surfing peers.
"An incredible human being!" wrote Carlos Burle
, another top Brazilian surfer, in a post on Instagram
. He said dos Santos had "a whole life ahead of him."
"RIP Ricardo dos Santos. Forever in our hearts," tweeted Tiago Pires, a leading Portuguese surfer.
Dos Santos was "a fearless, world-class tuberider" who "captured the surf world's attention" at the 2012 Billabong Pro event in Tahiti, according to Surfer magazine
The off-duty police officer shot dos Santos three times in the chest Monday after the two had an argument in front of the surfer's family home in the Brazilian state of Santa Catarina, according to CNN affiliate Record News.
Doctors carried out surgery four times to try to save him, the broadcaster reported.
As his life hung in the balance, many of his friends and fans took to social media, pulling for him to make a recovery. Some urged people to make blood donations.
"We're all together with you, brother," Burle wrote on Instagram.
But the doctors couldn't stop the bleeding. Dos Santos died Tuesday.
"We need to pray and thank God for the time he lived among us," his father said. "A great athlete, he was an example."
The police officer suspected in the shooting, identified as Luis Paulo Mota Brentano, has been arrested but says he shot the surfer in self-defense, according to Record News.
Many in the surfing community found it hard to grasp what had happened.
"He represented all of us very well and was very well recognized for his hard work and also was a very good person," said Gabriel Medina, Brazil's first surfing world champion. "There are certain things that we do not understand."
Adriano de Souza, another Brazilian pro-surfer, said it was difficult to find words for the situation.
"What to say when you lose a great friend?" he asked in Facebook post. "What to say when you lose somebody as happy, good-hearted and at one with life as Ricardo?"