A fifth person is being questioned in relation to a shooting at a hotel carpark in Kilmainham last year.
Gary Carey died after being shot six times in the underground carpark last June.
A man in his 20s was arrested last night and taken to a city centre garda station.
Two men, in their 20s, and two women, in their 20s and 30s, arrested on Monday morning all remain in custody.
They are being detained under Section 50 of the Criminal Justice Act 2007 in various Garda stations across Dublin city.
Follow @98FM on Twitter for the latest Dublin news
