Police investigating the murder of Sean Fox are exploring the possibility that five other fatal shootings in recent years have been carried out by the same gunmen.
Mr Fox was gunned down as he watched a football game in the social club of Donegal Celtic on Sunday.
Police are investigating a potential link to the killing and five others.
Detective Superintendent Eamonn Corrigan said: "We are pursuing various lines of enquiry, and various hypotheses.
"We are looking at previous shootings to see if they are linked.
"As this is an ongoing investigation, I cannot comment any further on that at this time."
Detectives said they are following several lines of inquiry, including Mr Fox's friendship with another murder victim Jim Donegan, who was gunned down outside a school in Belfast in December 2018.
Mark Hall was fatally shot at his home in Rodney Drive in Belfast in December 2021, while 28-year-old Warren Crossan was murdered in Belfast in June 2020.
Robbie Lawlor, from Coolock in Dublin, was targeted at a house on Etna Drive in Belfast in April 2020, and Tommy Crossan was shot dead on the Springfield Road in Belfast in April 2014.
Detectives from the PSNI major investigation team probing the shooting of the 42-year-old have also revealed that a reward of up to £20,000 has been offered for information which leads to a conviction.
CCTV images show two masked men in hooded tops entering the grounds of the Donegal Celtic Sports and Social Club moments before Mr Fox was shot.
They are later seen running from the club.
Police also revealed that the two gunmen fired 20 bullets at Mr Fox and stood over him as he collapsed.
Making a public appeal for information and revealing the reward offered by Crimestoppers, Detective Superintendent Eamonn Corrigan said: "On Sunday afternoon, at around 2.25pm, two masked gunmen entered the Donegal Celtic Sports and Social Club on the Suffolk Road in west Belfast and made their way past several people.
"Sean Fox, who was a married father of two and a regular visitor to the club, was singled out as he sat enjoying a drink in a busy function room.
"He was shot multiple times by both gunmen.
"At one point, both gunmen stood over Sean, shooting him, as he collapsed to the floor.
"It was carried out in broad daylight and in the presence of others.
"The gunmen arrived, carried out the murder and left the club in under a minute.
"They were inside the premises for approximately 21 seconds."
The detective said the killers left on foot along the Suffolk Road in the direction of Gweedore Gardens.
He added: "This is a popular local club used widely by local families with young children.
"The gunmen fired 20 bullets and we have identified multiple strike marks.
"Anyone in that room or indeed nearby could have been killed or seriously injured on Sunday.
"This cold-blooded act has taken a man's life. It has left a family bereft and many others in the local community shocked.
"This barbaric act has no place in society."
Mr Corrigan continued: "I am asking anyone with information to please get in touch.
"Were you in the social club on Sunday afternoon? Did you witness the incident or see the two masked men arrive or leave the club?
"Were you in the surrounding area at the time? If you have any information or if you have any mobile or dash cam footage please contact us on 101.
"One suspect is a man of athletic build. He was wearing a blue hooded top, a peaked baseball cap, dark face covering, two-toned gloves (pale on top and dark on the bottom), dark-coloured bottoms and dark shoes/trainers.
"The second suspect is also a man of athletic build and was wearing a distinctive light (possibly grey) hooded top with three red lines down each arm, a peaked baseball cap, a light-green face covering, two-toned gloves (pale on top and dark on the bottom), dark coloured bottoms and dark shoes/trainers.
"If anyone wants to stay anonymous they can give information to the independent charity Crimestoppers on freephone 0800 555 111 or online at www.crimestoppers-uk.org. There is no caller line display, no 1471 facility and computer IP addresses are never traced or provided to detectives."
Additionally, information can be provided to police through the major incident public portal link: mipp.police.uk/operation/PSNI22R23-PO1.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know.