A man has been arrested by gardai investigating the murder of Andrew Allen in Co Donegal.
The 24-year-old victim, who was from the Top of the Hill in the Waterside area of Londonderry, was one of a number of people intimidated out of the city by dissident republicans.
He had moved to the Links View estate in Buncrana, where he was gunned down through a window after a group of men tried to break down the front door.
The attack, which took place on February 9, was blamed on the Republican Action Against Drugs group.
A Garda spokesman said a man in his 30s was arrested on Sunday morning in Co Donegal.
He is detained under Section 30 of the Offences Against the State Act 1939 at Buncrana garda station.