A man shot dead at a house in what police described as a "targeted attack" is reported to be convicted criminal and former mayoral candidate Paul Massey.
The body of a 55-year-old, named in local tributes as Mr Massey, was found at a property in Clifton, Salford on Sunday evening.
Security has been stepped up in the area and Manchester Road remains closed.
The victim has not been formally identified, police said.
Mr Massey, who had been a well-known security firm boss, was jailed for 14 years in 1999 for stabbing a man in the groin.
During sentencing the judge described Mr Massey as being "no stranger to violence".
He had been dubbed "Salford's Mr Big" by a councillor seven years earlier following disturbances in the city.
A friend of the victim spoke of his shock at the death.
Sean Casey told the Manchester Evening News: "Paul was a good friend. We would meet up every now and then and go for a drink. I've been ill recently and he was great.
"I'm just shell-shocked. It's just gutting. I wanted to pay my respects somehow so I brought some flowers down."
Others paid tribute online. One woman said: "R.I.P Mr Paul Massey sad sad day in Salford."
A neighbour wrote: "R.I.P Paul Massey! Scary to think he was shot like near my house thoughts are with friends and family."
Mr Massey had pledged to "really make a difference to the good people of Salford" when he ran for the position of mayor in 2012, but he failed to be elected.
Detective Chief Superintendent Russ Jackson of Greater Manchester Police appealed for anyone with information about the shooting to come forward.
He said: "People will understandably be alarmed when they hear about this incident which we believe was a targeted attack.
"I would like to reassure the public that we have a heightened level of police officers in the area while we establish the full circumstances of the incident and identify those responsible.
"We are actively following a number of lines of enquiry however, I would urge the local community to come forward if they saw or heard anything in the area.
"I urge anybody with any information about what's happened to come forward. I want to stress that any information received will be treated in the strictest confidence."
Greater Manchester's police and crime commissioner appealed for calm in the wake of the shooting.
"As horrendous as this most certainly is, the police will be working to make sure that ordinary members of the public can go about their business with a proper sense of security," he told the Manchester Evening News.
"Clearly no-one wants to see any further retaliation. The right answer for this is for people to come forward and help the police to arrest those who are responsible - because that's what will put a stop to guns in Salford."