The gunman, from Dublin, is understood to have been hired by another London family as part of a long-running feud.
The shooting took place on Wednesday morning when the gunman, hiding inside a parked van, shot Tony Brindle outside his house in Rotherhithe, south- east London.
Undercover officers and police marksmen who were waiting near by shot the gunman as he leapt out of his vehicle and fired again at Mr Brindle.
Both men were taken to hospital. The 49-year-old gunman, who had chest, arm and leg injuries, was stable but critical yesterday after undergoing surgery. Police have yet to interview him.
Mr Brindle, 30, whose brother was murdered in a gangland pub shooting, was comfortable in hospital after suffering stomach and leg injuries.
It emerged yesterday that the South East Regional Crime Squad and the Metropolitan Police's firearms unit, SO19, had been tracking the suspected hitman for some time after receiving a tip-off from Irish police that he had been hired by a family involved in a long running dispute with the Brindles.
The police had also been keeping Tony Brindle, a market trader, under surveillance for several weeks, believing he was the target of the attack.
The gunman is believed to come from north Dublin. Sources say he is not a member of any Irish terrorist organisation. A police source said: "He was brought over to London for a specific job. This is a tit-for-tat affair."
The shooting has sparked fears of renewed gangland violence in the capital.
In March 1991, Ahmet "Abbi" Abdullah, a cousin of the notoriously violent Arif family, was shot dead in a betting shop in Walworth, south London.
Five months later, David Brindle, brother of the man shot yesterday, was murdered in a pub by two gunmen in south London. An innocent bystander was also killed in the hail of bullets. One of the killers shouted "This is for Abbi" before firing.
In May 1992, Tony Brindle and his brother Patrick were charged with the murder. Both men were cleared.
In June 1993, Jimmy Moody, who many believe was responsible for killing David Brindle, was shot dead in east London.Reuse content