A 41-year-old Liverpool criminal - one of the two gunmen in the brutal feud-related murder of dissident republican Michael Barr - is also being investigated by gardaí over the shooting of The Monk's brother, Eddie Hutch.
The Herald can reveal that the investigation into David Hunter found he flew into Dublin from the UK on the morning of February 8, 2016 - the day that Eddie Hutch was murdered.
Gardaí have also found that Hunter flew back out of Dublin Airport the following day.
"This flight pattern is definitely suspicious to say the least, considering all that gardaí know now about David Hunter," a senior source told the Herald.
"He was in the country for not much more than 24 hours and in this timeframe the murder happened.
"He is being looked at for having had some role in the Hutch murder, but it has not yet been established what part, if any, he played," the source said.
Eddie Hutch Snr (58) was shot dead at his home in Poplar Row, Ballybough, in Dublin's north inner city on the night of February 8 in revenge for the Regency Hotel bloodbath that had happened just three days earlier.
There were a number of gunmen involved in the murder and there have been some significant arrests, but no charges yet.
Meanwhile, the Herald can also reveal that gardaí have identified a third suspect in the Michael Barr murder - the suspected getaway driver.
"This investigation is far from over - a third suspect is expected to be arrested in the coming months," the source said.
Convicted woman-beater David Hunter entered the Sunset House in north inner city Dublin when he and Eamon Cumberton (32) fired multiple shots at Barr (35), who was working in the pub on the night.
The victim, who was well known to gardaí, was hit seven times.
Barr, a New IRA figure from Strabane, Co Tyrone, was blamed by the Kinahan cartel for sourcing the weapons used in the Regency Hotel attack in which key cartel player David Byrne (34) was shot dead.
Sources said last night that they were unaware how much Hunter was paid for his role in the murder of Barr - one of 18 linked to the deadly Hutch/Kinahan feud.
Hunter has been in custody on the Barr murder charge since March 2019 when he was arrested on foot of a European Arrest Warrant as he left Wormwood Scrubs Prison in London.
Hunter, from Huyton, Mereyside, beat up his girlfriend and threatened to kill a member of her family in Liverpool in 2016 before going on the run.
He was convicted of actual bodily harm in 2017 and jailed for 15 months.
Hunter now faces the mandatory term of life in prison after being convicted of murder yesterday at the Special Criminal Court.
Presiding judge Mr Justice Alexander Owens said that the evidence had been heard in a "compelling way" that Hunter was one of the two gunmen who entered the Summerhill pub on April 24, 2016, and murdered Barr by shooting him.
Hunter's involvement in the murder had been "fully proved" and the three-judge court was "sure of his guilt", he remarked.
The judge noted that the major part of a DNA profile taken from a ski-mask recovered during the investigation into the shooting of Barr matched and verified the profile of Hunter.
The circumstantial evidence in the case "pointed inextricably" to Hunter's guilt and the facts taken together had established the father-of-five's guilt beyond a reasonable doubt and no other rational explanation could be drawn, indicated the judge.
Mr Justice Owens said the court rejected Hunter's explanation for his whereabouts on the night.
He also said the whole story of how Hunter came to lose his ski-mask "did not have a ring of truth about it" and there was no doubt that it was put into the car to either use at the murder or in the getaway car.
In a voluntary statement to gardaí, Hunter said that the ski-mask was his but that he had dropped it in a car driven by another man when he visited Ireland two months before the murder on a car-stealing exercise.
Hunter claimed he had used the mask on various ski trips with his children to Norway, France, Spain, Scotland, Austria and Switzerland.
A number of holiday photos of Hunter in a ski mask were handed into court during the trial.
"The DNA material attributed to Hunter and the matching DNA profile itself established a strong probability that Hunter was one of the murderers in the car," said the judge, adding that it was not a "credible explanation" that the ski-mask had been left behind by him on a previous trip to Dublin.
Barr was shot seven times after two armed men wearing boiler suits and full rubber masks over their faces entered the Sunset House pub at around 9pm.
He had been shot five times in the head, once in the leg and once in the shoulder.
Then-deputy state pathologist Dr Michael Curtis found that the cause of death was multiple gunshot wounds.
During the five-week trial which ended in July, evidence was given that at around 9.20pm at Walsh Road in Drumcondra, a silver Audi A6 was seen to arrive and that three occupants got out and set the car alight.
The three men then got into a "possibly silver" Ford Mondeo and left the scene and gardaí already in the area arrived at 9.42pm and put the fire out. The burning Audi A6 vehicle was examined and cocked and loaded weapons, ready for use, were found.
Boiler suits, two ski masks and two rubber masks were also found in the rear seat.
A phone, which had a number of missed calls, was found next to a bullet on the grass nearby.
During the trial, Dr Edward Connolly of Forensic Science Ireland testified that mixed DNA profiles had been found on two masks taken from the Audi by gardaí.
The expert witness said that he found a mixed DNA profile on a ski-mask with four elements; one major, two minor and one trace. The "major contributor" of the ski-mask's DNA profile formed 61pc of the mixed profile, he said.
DNA samples from an apple core and a cigarette butt discarded by Hunter in the course of his extradition from the UK and his processing in Ireland on October 16, 2019, were also cross-referenced.
The witness testified that the odds on the profile created by the cigarette butt and the apple core being of an individual unrelated to the DNA on the ski-mask were "a thousand-million to one".
Mr Justice Owens will hand down the mandatory sentence of life imprisonment on November 2 and remanded Hunter in custody until that date.
Barr was a close pal of Kevin 'Flat Cap' Murray who died from motor neurone disease aged 46 in August 2017.
Murray gained his nickname after he was photographed running from the hotel where David Byrne was murdered wearing the distinctive hat and carrying a gun.
Barr, who was living in Finglas, was due to be sentenced three days after he was killed at the Special Criminal Court for handling stolen property.
Earlier that month he pleaded guilty at the Special Criminal Court to handling stolen electrical equipment at Finnstown House Hotel in Lucan.
Speaking outside the Criminal Courts of Justice, Colin Barr, the dad of the victim, said the verdict gave the family "some satisfaction" that Hunter "was going behind bars".
He said organised crime "has got no place in Ireland" and "without the gardaí these people would not be behind bars" and added that Hunter had been "found guilty for all his lies".