A man in his 50s, who was being questioned over the murder of Londonderry man Andrew Allen in 2012, has been released without charge.
He was arrested in Donegal on Saturday night.
The father of two was shot dead at his home in Buncrana, County Donegal, in February 2012.
Republican Action Against Drugs (RAAD) admitted responsibility for the murder. Mr Allen's family have always denied claims he was a drug dealer.