The Continuity IRA (CIRA) has warned of a reign of terror after admitting its gunmen killed David Byrne during the boxing weigh-in at the Regency Hotel in Dublin.
A member of the Republican splinter cell told the BBC : "This will not be an isolated incident. Continuity IRA units have been authorised to carry out further operations. More drug dealers and criminals will be targeted. The Continuity IRA will carry out further military operations."
He also claimed Bryne was shot over his alleged involvement in the murder in 2012 of Real IRA member Alan Ryan. The 32-year-old was blasted several times at Grange Lodge Avenue in Clongriffin. He had previously been convicted of running a Real IRA training camp.
The shooting happened on Friday 5 February at 2.30pm at the hotel, on the Swords Road, during a weigh-in for Saturday's WBO European Lightweight title fight between Jamie Kavanagh v Antonio Jao Bento. It was part of an event called "Clash of the Clans" at the National Arena in Tallaght.
Byrne, 33, from Raleigh Square in Crumlin in the south of the city, was one of three men shot when up to a least four gunmen - one of whom was dressed as a woman - stormed the hotel in police-style uniforms armed with AK-47s.
The Irish police, An Garda Síochána, had been investigating the shooting was fallout from a gangland feud. But the development points the investigation in a different direction.
Who are the Continuity IRA?
Formed in 1994, the Continuity IRA (CIRA) is the terror unit of the Republican Sinn Fein (RSF) - itself a Sinn Fein splinter group.
Like the IRA, it's aim is to force the British out of Northern Ireland and has been responsible for bombings, assassinations, kidnappings, extortion, and robberies.
The group, which is believed to have support from sympathisers in the United States, has failed to observe a cease-fire and said disarmament would be "an act of treachery".
In 2009 it killed two British Soldiers and Constable Stephen Carroll in an attempt to destabilise the peace process.