He was taken to hospital but was declared brain dead hours later.

Lo was one of the most successful Brazilian Jiu-Jitsu athletes of all time, having won eight World Championships as a black belt since 2012. Earlier this year, he won another World Championship in California.

The killing allegedly took place during a confrontation between Lo and Police Officer Henrique Otávio Oliveira Velozo, according to a report by MMA Fighting.

Witnesses said Velozo grabbed a bottle from Lo’s table and that the fighter took the cop down and held him, according to the outlet, citing a police report.

MMA Fighting reports after the pair were separated, Velozo allegedly pulled out a gun, firing a round into Lo’s forehead.

Tributes came flooding in after the shock news of his death.

“A very sad day for the BJJ community,” analyst and former UFC fighter Kenny Florian tweeted. “Leandro was a legend.”

Combat sports analyst Luke Thomas tweeted: “Oh my god.”

UFC commentator John Gooden tweeted: “Saddened to hear about the tragic loss of Leandro Lo. One of the greatest Jiu-jitsu players ever. Absolutely tragic. My condolences to his family and friends.”