Roy Collins, 35, was shot dead on Holy Thursday in 2009 as he worked at the family business in Roxboro shopping centre.
Gardaí believe it was a revenge attack for evidence given by a family member which led to Dundon, of the McCarthy/Dundon gang, being jailed.
Dundon was convicted of threatening to kill Mr Collins’ cousin Ryan Lee, and was jailed for 10 years in early 2005, a sentence later reduced to seven years by the Court of Criminal Appeal.
Mr Lee had been shot and badly wounded after he turned away Annabell Dundon, the 14-year-old sister of the notorious crime boss, from the Pike Inn bar due to her age.
Mr Lee, in evidence, said Dundon pointed his hands like a gun at him and said: “F**k you, you’re dead.”
Half an hour later, Mr Lee was singled out by a gunman wearing a motorbike helmet and shot twice as he stood behind the bar counter.
Having served out four years and 11 months of the seven-year sentence, Dundon was freed yesterday morning.
Last night Steve Collins, Roy’s father, said Dundon’s release was a big worry for the family. “You just don’t know what these people are going to do. He served almost five years but it is not enough. It is very worrying for us but we will have to deal with it.”
Mr Collins said he did not know if his family would be targeted again.
“People like that are very unpredictable. We will have to watch ourselves. We hope gardaí will be keeping an eye on him. It’s not him we have to be afraid of, but who he gets to do things for him. Now that he is out, it is easier for him to arrange things.”
In a surprise move, Dundon was released from the Dublin jail at dawn. Prison sources said he was let out of Wheatfield Prison just before 6am for “security reasons”. Prisoners are traditionally released after 8am at normal jail operating hours.
Prisoners in Ireland have a right to remission of one-quarter of their prison sentence. However, part of this remission may be cancelled as disciplinary punishment. Whether or not they get remission depends on good behaviour while they are in prison.