A former British heavyweight boxer was shot when he asked customers at a club to stop smoking.
The shooting is being investigated by Operation Trident detectives
James Oyebola, 47, is critically ill in hospital after being shot in the head and leg at Chateau 6 in Fulham Road, in south-west London.
Three men were seen running away after the 6ft 9ins tall former fighter, from north-west London, was shot.
Police said Mr Oyebola was involved in an altercation about smoking in the rear garden before being shot.
A search of the area was undertaken by police, including armed officers, following the shooting in the early hours of Monday.
The shooting is being handled by detectives from Operation Trident, which investigates gun crime in the black community.
Det Ch Insp Scott Wilson said police believe the three black suspects, aged between 19 and 25, ran from the club in separate directions.
"The altercation takes place, someone pulled out a gun and shots are fired, I can imagine it was over in 20 seconds," DCI Wilson said.
"It is a horrible crime to happen anywhere but over nothing - an incident such as smoking - these people need to be caught," he said.
In a statement Mr Oyebola's family thanked friends and fans for their "unprecedented show of support for James's well being".
Mr Oyebola's former manager, Frank Maloney, described the boxer as a "gentle giant" and said he had done a lot of work in the community to get youngsters into boxing and sport.
"I was absolutely devastated, struck dumb when I heard the news," he told BBC London.
The British Boxing Board of Control paid tribute to the former heavyweight champion, turned manager.
General secretary Simon Block said Mr Oyebola was "one of nature's gentlemen" and the shooting was a "cowardly and gutless attack".