An officer in the Northern Ireland Prison Service has died in a shooting incident on the M1 motorway in Co Armagh.
David Black, 52, was driving to work at Maghaberry high-security prison when he was ambushed on a stretch of road between Lurgan and Portadown at about 7.30am.
It is believed another car pulled up alongside the prison officer and several shots were fired into his vehicle, which careered off the road and crashed.
When emergency services arrived at the scene they found Mr Black dead inside the car. It is not clear if he died from gunshot wounds or from the impact of the crash.
A car suspected of being linked to the shooting was found burnt-out in the Lurgan area a short time later.
Mr Black, from Cookstown, Co Tyrone, had over 30 years' service in the Prison Service and was nearing retirement.
Local DUP MP Jeffrey Donaldson said he believed dissident republicans were behind the murder.
Dissident republican prisoners in Maghaberry prison have been involved in a long-running and bitter dispute with the prison authorities over conditions in the jail.
PSNI Assistant Chief Constable Drew Harris said the gunman was in a Toyota Camry with a Dublin registration, which drew alongside Mr Black's black Audi.
"From that car it appears that shots were fired at Mr Black," he said.
"Almost immediately his car veered off the motorway and into a pretty deep drainage ditch.
"Mr Black appears to have sustained very serious and probably fatal gunshot wounds."
Mr Black, who was married with a family, was the 30th prison officer killed in Northern Ireland since 1974.
No return to 'violent days'
President Michael D Higgins said the murder must not deter the efforts of all sides to fully consolidate peace "on our island and achieve and shared and reconciled society".
Mr Higgins spoke with Northern Ireland's Justice Minister David Ford and asked him to convey his deepest sympathies to Mr Black's family and his colleagues in the NI Prison Service.
Tánaiste Eamon Gilmore condemned the shooting and said there would be "no return to the dark and violent days of the past".
Minister for Justice Alan Shatter condemned the "brutal and barbaric murder" of the prison officer.
He said he had spoken to Mr Ford and Secretary of State Theresa Villiers and expressed his sympathy and that of the Government to Mr Black's family and colleagues.
Northern Ireland First Minister Peter Robinson and Deputy First Minister Martin McGuinness issued a joint statement saying their thoughts and prayers are with the bereaved family.
They said: "Actions like this have no place in society and those who carried out this murder have nothing positive to contribute, and we refuse to let the people behind this attack divert us from building a better and peaceful future for everyone."
British Prime Minister David Cameron said the killers would not deny "the people of Northern Ireland the peaceful, shared future they so desperately want."
He offered his condolences to Mr Black's family and said: "First and foremost, this is a dreadful tragedy for the family and friends of David Black, who has been so brutally murdered as he went about his work keeping the people of Northern Ireland safe. My heart goes out to them".
Mayor of Craigavon Carla Lockhart said the shooting was totally unjustifiable and has stunned and shocked all communities.
Sinn Féin Assembly member John O’Dowd said the people responsible or those who act as their political spokespeople need to explain themselves to the community.
The Grand Master of the Grand Orange Lodge of Ireland, Edward Stevenson, described those responsible as cowardly and faceless terrorists.
Mr Black had been a member of the Montober Lodge and had played in a flute band.