Four people being held in connection with the murder of Darren Guerrine have been released without charge.
A file will be prepared for the Director of Public Prosecutions.
Two men and two youths were arrested on Monday and were being questioned over the death of the 21-year-old, who was shot once in the back of the head with a shotgun in February.
He was found at the back of the Jamestown Industrial Estate along the Grand Canal by a man on his way to work on 18 February.
