Gardaí investigating the murder of Eamon Kelly were today carrying out evidential searches at two sealed-off crime scenes in Dublin.
The convicted criminal was killed near his home in Killester in Dublin yesterday afternoon.
He was shot at least three times in the chest.
A 33-year-old Dublin man, known to gardaí for his involvement in dissident republican activity, was arrested a short distance from the scene and is being questioned at Clontarf Garda Station.
The area on Furry Park Road where Kelly, 65, was shot, and Stiles Court where the gunman's suspected getaway car was found, were sealed off as crime scenes.
A black Lexus, registration number 96-D-27994, was found partially burned out in a cul-de-sac.
Gardaí have appealed for anyone with information to contact them.
Detectives are trying to establish a motive for the murder but believe it is connected to ongoing tensions between dissident republicans and criminal gangs, which led to the murder of the Real IRA member Alan Ryan three months ago.
The murder is the 15th gang-related killing this year.