The brutal murder of Sean Fox - who was gunned down as he enjoyed a drink while watching a football game at a social club - may be linked to five other executions, police believe.
Mr Fox was gunned down in what police described as a “calculated, planned and ruthless execution” in Donegal Celtic FC social club in west Belfast.
Police revealed the two gunmen opened fire 20 times in just 20 seconds and were in the bar for just under a minute on Sunday afternoon.
At one point both gunmen stood over Sean Fox, shooting him as he collapsed on the floor.
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."
The fatal shootings of Jim Donegan, Mark Hall, Warren Crossan, Robbie Lawlor and Tommy Crossan are explained below.
James, known as Jim, Donegan was murdered outside his son’s school in west Belfast on Tuesday, 4 December 2018.
CCTV of the shooter released by the PSNI at the time showed the gunman walking alongside unsuspecting pupils before opening fire.
Police investigating Mr Donegan's death have made multiple arrests, but nobody has ever been charged with his murder.
The investigation remains ongoing.
Mark Hall, 31, was murdered in a gun attack in west Belfast in December 2021.
Mr Hall was shot at his family home in Rodney Drive in Belfast on Saturday 18 December.
Just after 4.30pm, Mark’s sister, who was returning from the local shops, saw the gunmen approach the house and tried to intervene before a number of shots were fired through the front window striking and fatally wounding Mark.
A number of family members were present in the room when the shots were fired, all narrowly missing injury.
As the gunmen made off, a shot was also fired at Mark’s sister which passed through her handbag.
Mark was taken to hospital and despite the efforts of medical professionals, he died a short time later as a result of his injuries.
Detectives from the Police Service’s Major Investigation Team investigating the murder released CCTV footage and asked the public for help in the wake of the murder.
Multiple arrests have been made in connection with the murder, but nobody has ever been charged.
Warren Crossan, 28, was murdered in Belfast in June 2020.
The young father of 2 was shot dead in broad daylight in St Katharines Road, on June 27 2020, when two gunmen chased him and fired a number of shots in the busy residential area.
Police said he was shot a number of times at close range, and that the area was busy with pedestrians and motorists at the time of the shooting.
Detectives investigating the murder have released CCTV footage of the two suspects, but nobody has ever been charged with the fatal shooting.
Robbie Lawlor, from Coolock in Dublin, was targeted at a house on Etna Drive in Belfast on Saturday 4 April 2020.
According to police, a single gunman emerged from the house and opened fire in broad daylight.
Detectives know a white Volkswagen Scirocco, registration YLZ7052, found burned out in Kingston Court on the day of the murder was parked at Estoril Park a day earlier.
It had been stolen in the Republic of Ireland on 30 January 2020.
Police investigating the murder also appealed for information about a “hooded man” spotted close to the scene.
Originally from Dublin, Lawlor, 36, had been heavily involved in a bitter dispute between rival Drogheda-based factions.
Previous court hearings were told he may have travelled to Northern Ireland because he feared he was going to be attacked as part of a deadly drugs feud.
But his assassination had already been commissioned three weeks earlier at a meeting in a Sligo hotel attended by an international drug dealer, it has been claimed.
While multiple arrests have been made in connection with the murder, no one has ever been charged with the fatal shooting.
Tommy Crossan, 43, was shot dead at a fuel depot off the Springfield Road on Good Friday 2014.
At the time, there were suspicions the murder was linked to a long-running dispute with rival dissident republicans.
The father-of-six, who was a former senior member of the Continuity IRA (CIRA), was gunned down at a fuel depot in the grounds of an industrial complex in full view of surrounding houses.
Police at the time also wanted information about a red BMW, registration OEZ 9177, which is believed to be linked to the murder. It was found burned out a short time later in the Beechmount Grove area of Belfast.
No-one has ever been convicted of the killing.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know.