A man is being held by Garda as part of an investigation into the 2013 murder of Dean Johnson.
The 31-year-old was taken into Garda custody Tuesday evening and is being detain in the Lucan Garda station under section 30 of the Offences Against the State Act 1939.
A woman (31) was also arrested but was later released without charge.
Three men were seen running from a black Vauxhall Vectra car around the time of the shooting.
The vehicle was later discovered on fire in a nearby housing estate.
Previous investigations into the murder of the 21-year-old has led to the discovery of a sawn off shotgun, ammunition and drugs.