Update 9.30pm: A man in his late 20s who was arrested this morning in relation to a fatal shooting in Citywest Shopping Centre on 18 September 2017, has been released without charge.
A file will be prepared for the Director of Public Prosecutions.
Update 6pm: A man in his 20s is being held in Dublin in connection with the shooting of a man in September 2017.
He is being held at Tallaght Garda Station.
28-year-old John Gibson was shot on Fortunestown Lane in Tallaght two years ago.
The fitness instructor died at the scene after being treated for gunshot wounds.
This morning, gardaí arrested a man in his late-20s in connection with the incident.
He is the fourth person to be arrested in the investigation.