Three local men and a woman have been arrested for questioning by gardai investigating the fatal shooting of Jamie Lindsay in Athy, Co Kildare.
Lindsay (20) was shot at close range in the face after he was lured by a text message to a meeting with his killers.
Gardai have also seized a silver Toyota Avensis car, which they believe could be linked to the shooting, and it will undergo forensic tests over the weekend.
Officers believe Lindsay was shot dead as a result of a row over a drugs debt.
Last night three men, aged from 19 to 20 years, and a 21-year-old women, were in garda custody.
They were detained yesterday afternoon in the Athy area under section 50 of the anti-gangland legislation, the Criminal Justice Act, 2007, and can be held without charge for up to a week.
The suspects are being questioned at Naas, Newbridge, Kildare and Leixlip stations.
Gardai have not yet found the shotgun used in the attack in the Coneyboro estate in Athy last Saturday night.