Brazilian jiu-jitsu great Leandro Lo, an eight-time world champion, was fatally shot in a Sao Paulo club Sunday, his family's lawyer said.

An off-duty police officer has been arrested for allegedly shooting the 33-year-old martial arts champ, after turning himself in to the authorities, local media reports said.

Lo was out with friends for a concert at the Clube Siria, a sports and social club in Brazil's biggest city, when the attacker approached their table and began making threatening gestures with a bottle, said lawyer Iva Siqueira Junior.

Lo, who won International Brazilian Jiu-Jitsu Federation (IBJJF) world titles in five different weight classes from 2012 to 2022 -- an all-time record -- pinned the man to the ground "to stop the situation and avoid a fight," Siqueira said.

He said Lo's friends then helped both men up and urged the attacker to calm down and leave.

"At that exact moment, the guy allegedly turned around, pulled out a gun and shot Leandro in the head," Siqueira told AFP.

The jiu-jitsu champion was rushed to hospital, but was pronounced brain dead, he said.

A Sao Paulo court ordered the 30-year-old suspect detained for 30 days pending further investigation, newspaper Folha de Sao Paulo reported.

There was an outpouring of condolences from jiu-jitsu fans on social media.

Specialty site BJJ Heroes called Lo "one of the best pound-for-pound grapplers to have ever graced a mat."

With roots in Japanese judo, Brazilian jiu-jitsu developed in the South American country in the early 20th century, and is one of the most popular full-contact sports, featuring prominently in mixed martial arts (MMA) competitions.