Boxer James Oyebola, who was shot outside a south London club after asking three men to stop smoking, has been described as "a first-class family man and a wonderful role model".
Oyebola won the British title by battering Derby's Clifton Mitchell in 1994
His former manager, boxing promoter Frank Maloney, was at his bedside at Charing Cross Hospital when Oyebola was pronounced dead at 1239BST.
He said: "James had to fight tooth and nail for everything he achieved in life and then he dedicated himself to encouraging young kids to do the same.
His biggest fights
6 May 1994 - knocked out Brighton's Scott Welch to win WBC international heavyweight title
19 Nov 1994 - KO'd unbeaten Clifton Mitchell from Derby to win British crown
27 Oct 1995 - Stopped by Scott Welch in rematch
28 Sep 1996 - Beaten by Londoner Julius Francis in his last fight
"This is one of the saddest times I have ever experienced. Boxing has lost a great ambassador and it is awful that a guy like James should have been the victim of such a cowardly attack."
Oyebola won 18 of his 23 fights, and was also a bronze medallist at the Commonwealth Games in 1986.
Maloney promoted the boxer after he took the WBC international title in Atlantic City in 1994, beating Scott Welch. He later took the British title off Clifton Brown.
His ring nickname was "Big Bad" James Oyebola.
But Mr Maloney said: "You could never associate the 'bad' with James. I only ever saw him get angry once.
"I was in his corner for his fight against Mitchell. He was doing badly and when he came back to the corner I threatened to pull him out. He said, 'if you do that I'll knock you out instead'. He went out and stopped Mitchell in the next round."
After his fighting career ended in 1996, Oyebola turned to managing and trained Ajose Olusegun, who won the Commonwealth title in London in June.
Former opponent Welch said: "He only phoned me two weeks ago and told me how well the family was doing and about the prospects he was managing.
"We didn't like each other at the time but after we fought there was a great mutual respect and admiration.
"He might have been big and bad inside the ring but he was a great family man out of it.
"To be killed like that by a bunch of cowards who would obviously never dare set foot in the boxing ring is disgusting and it makes me sick."