Police have arrested a man over the murder of prison officer David Black.
Mr Black, a 52-year-old father of two, was shot as he drove to work on the M1 in County Armagh on 1 November.
Mr Black had been driving to work at Maghaberry Prison, the North's high security jail, when he was attacked.
A new dissident republican paramilitary group calling itself the IRA admitted the killing. A 36-year-old man was arrested on Tuesday in County Tyrone.
He has been taken to Antrim police station for questioning about the murder.
Mr Black was the first prison officer to be murdered in Northern Ireland in 20 years.