Merseyside Police fear gang warfare is the reason why Joe Thompson was shot dead in the Norris Green area of Liverpool.
Thompson, 32, was shot at close range on Ravensthorpe Green in the heart of the Norris Green estate in the early hours of 14 June. A 27-year-old man was also shot and remains in a critical condition.
Thompson's son left a tribute to his father at the scene of the shooting, saying: "RIP dad GBNF (gone but not forgotten). I will miss you. From AT."
Thompson was a member of the notorious Norris Green Strand gang,rivals of the Croxteth Crew, the gang blamed for the murder of 11-year-old Rhys Jones in 2007.
Armed police are patrolling Norris Green amid fears of reprisal by the Strand gang, also known as the Nogga Dogs.
Police confirmed that Thompson's younger brother, Gerard, was shot four times in a murder attempt in Croxteth nearly two months ago.
A previous turf war between the gangs led up to the murder of 11-year-old Rhys Jones as he walked home from football practice. He was killed by 16-year-old Croxeth Crew member Sean Mercer.
Assistant Chief Constable Andy Ward told the Liverpool Echo: "We are still unsure of the motive for this murder, but we are having significant problems with interfactional disputes. The deceased has got a known criminal history.
"The risk is the potential for innocent people to be hurt as people in this city know all too well when Rhys Jones was killed.
"It's very difficult to say who belongs to a certain urban street gang. Alliances can change by the week."
The Liverpool Echo also reports that Thompson had also been a prime suspect in the murder of Croxteth Crew leader Danny McDonald, who was shot in Norris Green's Royal Oak pub on New Year's Day in 2004.
Thompson was eventually released and no one was charged with the murder, but Strand member Liam Smith was widely believed to be the killer.
Smith, 19, was shot dead outside Merseyside's Altcourse Prison on 23 August, 2006, in what was believed to be a revenge attack for McDonald's murder.