A man is being questioned by gardai about the gangland-style murder of a criminal in August.
The 22-year-old suspect was arrested in Dublin at approximately 11.30pm on Sunday night.
He was being detained at Finglas Garda station under section 50 of the Criminal Justice Act. in connection with the summer shooting.
Daniel Gaynor, who had convictions for drugs and firearms offences, was gunned down in front of his wife and two children in Finglas, north Dublin, on August 14.
Eye witnesses said the gunman fired several shots at Mr Gaynor as he walked towards the junction of Barnamore Crescent and Saint Helena's Road with his family.