A man who was murdered on a Dublin street on Monday was a convicted Real IRA man who is believed to have been the target of a criminal gang.
Alan Ryan, 32, was shot several times at Grange Lodge Avenue in Clongriffin at about 15:30 BST. A second man was also shot and sustained leg injuries.
In 2000, Ryan had been jailed over the discovery of a Real IRA training camp.
RTE's crime correspondent, Paul Reynolds, said he was shot in the head in a "planned, targeted killing".
He said the Dubliner was "very well known in criminal and republican circles both north and south of the border".
Mr Reynolds said the two men were walking along the street in north Dublin city when they were approached by a gunman who opened fire on Ryan first.
"He collapsed and then the gunman walked over and shot him in the head as he lay on the ground. He died instantly," he added.
The man who was with Ryan, believed to be from Sligo, was shot in the leg.
Two men believed to have been involved in the attack escaped in a silver Volvo car which was later found burnt out in a nearby graveyard.
Mr Reynolds said Ryan first came to the attention of Irish police in 1999, when they uncovered a Real IRA training camp in a underground bunker at Stamullen, County Meath.
Ryan was one of 10 people arrested in the raid.
Six months later he pleaded guilty to receiving training in the use of firearms at the camp and was sentenced to four years in prison.
The RTE correspondent said that after Ryan left prison, he became "involved in extortion, extorting money from businesses and from publicans" and "threats on drug dealers".
He said Ryan's faction within the Real IRA in Dublin had been feuding with major gangland criminals for some time.
He added that at the time of his death, Ryan was facing a charge of "demanding money with menaces from a Dublin publican in the north inner city" and had also served time for possession of a firearm in a separate case.
Mr Reynolds said: "Gardai are worried about the fact the republican groups don't tend to forget when members of their organisation have been shot and killed particularly by drug gangs or violent gangland criminals."
Mr Reynolds said there were increased police patrols in the area close to murder scene.
Irish police believe that at least two gunmen were involved in the shooting.