A long-serving prison officer has been murdered in a motorway ambush believed to have been carried out by dissident republicans in Northern Ireland.
David Black, from Cookstown, County Tyrone, had more than 30 years' service in the Prison Service and was approaching retirement.
He was ambushed by a gunman on Northern Ireland's M1 motorway early in the morning as he drove to begin duty at the top security Maghaberry jail near Lisburn, County Antrim.
Politicians on all sides condemned the murder and, even though no organisation has admitted responsibility, security chiefs believe republicans opposed to the peace process were involved.
The extremists have been involved in long-running protests against jail conditions inside Maghaberry.
The attack happened at the M1/M12 turnoff in County Armagh
Police Service of Northern Ireland (PSNI) Chief Constable Matt Baggott said: "It was a completely senseless attack. It demonstrated the recklessness and ruthlessness and sheer dangerousness of those who oppose peace and are dedicated to taking us back to those dark days of the past.
"This has all the hallmarks of dissident republicans. This was just a brutal attack and we need the public's support to be able to solve it as quickly as possible."
Police said the gunman was in a Toyota Camry with a Dublin registration which drew alongside Mr Black's black Audi. It appeared shots were fired at the prison worker from the vehicle, causing Mr Black's car to veer off the motorway and into a drainage ditch.
He "sustained very serious and probably fatal gunshot wounds," police said.
It is 18 months since renegade republicans claimed the life of police officer Ronan Kerr in Omagh, County Tyrone.
Mr Black had expressed interest in an early retirement scheme but his departure date had not been set, Prison Service director general Sue McAllister said.
Police attending the scene
Mrs McAllister said the Prison Service would not be bowed.
"We will not allow this to derail the efforts that we are making to reform the service but we will do everything we can to support all of our staff in the very difficult days ahead," she added.
A car used in the attack was later found burnt-out in Lurgan, Co Armagh, where supporters of dissidents have backed the jail protest campaign.
Mr Black, who was married with a family, was the 30th prison officer killed in Northern Ireland since 1974.
It is understood his service stretched back as far as the 1981 IRA hunger strike inside the Maze prison, when 10 republicans starved themselves to death.
Finlay Spratt, the head of the Prison Officers' Association, who knew Mr Black and described him as "a very nice fellow to work with", criticised the security provisions offered to prison officers since the Troubles ended.
Northern Ireland Secretary Theresa Villiers condemned the attack
"They have stripped away all the security around prison officers," he said.
Stormont First Minister Peter Robinson and Deputy First Minister Martin McGuinness condemned the murder.
"At this time, our thoughts and prayers are with the bereaved family and we condemn this murder in the strongest possible terms," they said in a joint statement.
The shooting happened at around 7.30am, at the same time as a major security alert further along the motorway at a shopping centre at Sprucefield, near Lisburn, where bomb disposal experts were called in to check a car.
It is believed this vehicle might have been linked to the shooting,
Only a day ago, Northern Ireland Secretary Theresa Villiers warned that the threat from dissident republicans in Northern Ireland remained severe.
The motorway was closed following the shooting
Ms Villiers described the attack as "cowardly and evil attack".
She said: "The thoughts and deepest sympathy of us all are with the family, friends and colleagues of the murdered prison officer.
"Like his colleagues across the prison service he was dedicated to serving the whole community in Northern Ireland . This is in stark contrast to the people responsible for this despicable crime.
"The British and Irish Governments, the Executive, the PSNI and Garda - and above all the people of Northern Ireland - will continue to work together to ensure that those who pursue their aims by violence will not succeed."
The Republic of Ireland's foreign minister Eamon Gilmore added his words of condemnation.
"I know that I speak for every decent man, woman and child on this island, North and South, in expressing revulsion at this act," he said.