Murder probe detectives have offered a £50,000 reward for information in the death of the businessman Paul Massey, dubbed "Mr Big".
Detective Chief Inspector Howard Millington of Greater Manchester Police said the reward was available for information leading to the conviction of the gunman, after the 55-year-old former convict was killed at his house in Salford on July 26.
Appearing on BBC's Crimewatch, Mr Millington said: "(The suspect) is described as a slim, white male wearing a fisherman style hat, a green long-sleeve top, some form of face covering and dark combat trousers tucked into lace-up boots.
"He was carrying a small black gun, similar to a sub machine gun, toward's Paul's address.
"The offender fired a series of shots at Paul and left the same way he came.
"That was the last sighting of him."
Mr Millington said a man was seen nearby two days earlier carrying a torch and an Uzi-style sub machine gun
The victim, a father of five, was a well-known figure in his home city of Salford, and had been involved in security firms operating in Manchester and beyond.
Massey was born and raised in the city and enjoyed a popular and fearsome reputation - despite being not much over five feet tall (1.5m) and continuing to live a modest life in his home town.
He had first been dubbed "Mr Big" by the late Salford councillor Joe Burrows at a town hall meeting to discuss civil disturbances in 1992. Massey denied having anything to do with the unrest.
Massey's reputation grew since the 1990s and he had reportedly in the past acted as a mediator between warring factions.
But in 1999 he was sentenced to 14 years after he stabbed a man in the groin, severing an artery, and apparently leaving him for dead outside a club in Manchester. At the time he was being filmed by a TV crew making a documentary about his life.
After the attack Massey fled to Amsterdam, but was extradited.
Since his release from Frankland Prison in County Durham, he is believed to have been involved in the security business and to have invested in property.
Massey was regarded as a "target" criminal by police, and he alleged that a branch of the MI5 security services working with police against organised crime was monitoring him.
In 2012 Massey fought a losing campaign to become the elected mayor of Salford - saying he would rid the streets of drugs.
He called on voters to forget his "Mr Big" reputation, that it was in the past and people had misjudged him.
However he was still under investigation earlier this year by police from the regional organised crime squad investigating allegations of money laundering.
He had been arrested with five others in December 2011 as part of a police probe in to a Salford-based security company.
Massey claimed the police were conducting a "witch hunt" against him and strenuously denied any wrongdoing after having his bail conditions relaxed.
Anyone with information concerning his death is asked to contact 101.