A 27-year-old man who was being questioned by the PSNI in connection with the murder of a Dublin criminal in Belfast at the weekend has been released without charge.
Two other men and a teenager are still being questioned over the shooting of Robbie Lawlor outside a house in the Ardoyne on Saturday morning.
The two men, aged 33 and 30, and the youth, aged 17, are being questioned at Musgrave police station.
The PSNI believes a single gunman fired several shots at Lawlor, who was a suspect in the murder of 17-year-old Keane Mulready-Woods from Drogheda earlier this year, but the murder weapon has not been recovered.
Searches were carried out yesterday in Belfast and Crumlin as part of the murder inquiry.
Lawlor, 35, was well known to gardaí for his involvement in serious and organised crime.
He had more than 100 previous convictions and had been released from prison last December.
The PSNI have appealed for witnesses or anyone with information to contact them.