A 22-year-old man was arrested in Northern Ireland today in connection with the murder of Constable Stephen Carroll by dissident republicans.
The PSNI officer was shot dead by the Continuity IRA as he answered a call for help in Craigavon, Co Armagh, in March last year.
The man, who are arrested in the Newtownabbey area, near Belfast, is being questioned at Antrim police station.
A teenager and a 38-year-old man are in custody charged with the murder.
Constable Carroll (48), was married and came from Banbridge, Co Down. He was killed two days after the Real IRA shot dead two soldiers outside Massereene Barracks in Antrim.