Video footage obtained by the Sunday World from inside Mountjoy Prison shows one of the Kinahan cartel's most feared gunmen laughing and joking about shootings.
A prison album of mob pictures taken in the high-security jail also shows how the same gunman, Trevor Byrne - who was chief suspect for the 2014 shooting of John Gilligan and who was quizzed over the murder of Eddie "Ned" Hutch (58) - is living the high life with his fellow Kinahan cartel inmates behind bars.
The exclusive video shows a Limerick criminal, who cannot be identified for legal reasons, mimicking a shooting with his hands shaped like a gun.
In the clip, Trevor Byrne (41) jokes 'no recoil on this' and the Limerick man sounds off four shots before the pair break into laughter.
"What way did you do him?" Byrne asks.
"With the big one, like this," the Limerick thug responds, before mimicking the noise of a machine gun.
Again, the pair, who are in a cell with a number of other inmates, burst into laughter.
Byrne then asks: "What way did you do the Mossberg?"
Mossberg is a company most well known for their shotguns, including the 500/590 pump-action and 930 semi-automatic shotguns.
"The Mossberg now would go bang," laughs another inmate.
"Wallop him out of it," responds the Limerick man.
An album of pictures from inside the prison also show how Byrne has linked up with a number of convicted members of the Kinahan cartel behind bars.
One picture shows how Byrne celebrated his 40th birthday in Mountjoy with a Who's Who of cartel criminals present in a cell.
The inmates pictured include Kevin Gibson, Graham Gardiner, Byrne himself, Glen Thompson, Robert Browne and a sixth inmate.
Kevin Gibson was jailed for seven years in 2015 for masterminding a €280,000 cocaine-smuggling operation.
Gibson from Drimnagh, south Dublin, was considered by gardaí to be a friend of senior cartel figure Liam Byrne.
Detectives believed Gibson was transporting the haul to a gang in the North with links to the Kinahans. He was regarded by gardaí as a "mid-level" cartel associate.
Kinahan quartermaster Graham Gardiner is serving a nine-year-sentence, handed down in May of last year for possession of a deadly cache of firearms.
Gardiner (36), from Cabra, in north Dublin, received the sentence after his DNA was found on three firearms recovered by the Garda National Drugs and Organised Crime Bureau on November 5, 2016.
During the Garda operation to target members of the Kinahan mob, officers recovered two MP9 sub-machine guns, one Magnum, two Smith & Wesson revolvers, two silencers and 107 rounds of ammunition.
Investigators believed the weapons were to be used to target a close associate of Gerry 'the Monk' Hutch.
Glen Thompson and Robert Browne, a former British Army soldier, were each sentenced to 12-and-a-half years and 11-and-a-half years jail time respectively for possessing weapons with intent to endanger life.
The pair were part of a three-man-team, which also included Glen's brother Gary, caught with a sub-machine gun and three handguns in a van in an underground car park 250 metres from the home of the planned "target", Patrick 'Patsy' Hutch.
The sixth inmate in the picture is serving six-and-a-half-years after being caught moving "lethal" ammunition and guns for "dangerous people" to whom he owed a drug debt.
We are not naming this inmate as prior to entering prison he was not classified as being a cartel associate.
Another picture obtained by this newspaper shows how, far from living a life of deprivation behind bars, Byrne clothes himself in designer Hugo Boss t-shirts.
Meanwhile, his cell is decorated with one poster of Walter White's catchphrase 'I am the one who knocks' from the hit TV show 'Breaking Bad'.
Byrne, from Cappagh Road, Finglas, Dublin, was found guilty of five charges last year related to a botched armed robbery at Boyle Sports in Applewood Village in Swords, Co. Dublin, as well as hijacking a woman's vehicle on March 19, 2010.
The verdict came months after Byrne, who has 41 convictions, received nine years after being caught with a handgun.
Byrne, who has been quizzed by gardaí in relation to Kinahan-Hutch feud attacks, has a history of involvement in organised crime.
The Sunday World previously revealed how John Gilligan blamed Byrne for hit attempts on him in 2013 and 2014.
Byrne and Gilligan had hated each other since serving time in Portlaoise Prison when Byrne gave Gilligan a beating.
Gilligan was the victim of two assassination attempts in 2013 and 2014. He believed Byrne was behind one attack, but Byrne never faced any charges over the incident.
Gardaí suspect Byrne was actively involved in the Kinahan-Hutch feud and quizzed him over gangland gun attacks, including the murder of Eddie "Ned" Hutch (58), who was shot dead in 2016 just days after the Regency Hotel shootings.
Byrne was arrested in May 2016 by gardaí investigating Mr Hutch's murder. He was questioned for several days before being released without charge.
He later left the country and was believed to be hiding in the UK. He then returned to Ireland and was arrested in a shed house in Woodford Grove, Clondalkin, on November 15, 2019, where gardaí found a 9mm firearm.
Last year, the Special Criminal Court found Byrne guilty of robbery, possession of a firearm, false imprisonment, threatening to kill and of unlawfully seizing a vehicle used in a getaway which were all part of the same botched robbery on the bookmakers in 2010.