Dissident IRA members shot dead a prison officer on the M1 motorway near Lurgan in County Armagh.
David Black, a member of the Orange Order, was gunned down when a car pulled alongside him and opened fire yesterday morning.
He was a prison officer at Maghaberry Prison where many dissidents are being held and some are on a “dirty protest.”
The Lurgan area is a hotbed of anti-peace process Republicans.
Sinn Fein’s Martin McGuinness, who is Northern Ireland’s Deputy First Minister, and DUP’s Peter Robinson, Northern Ireland’s First Minister, condemned the killing in harsh terms.
"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.
"There can be no justification for this brutal attack as this man was going about his daily life. People who work for the Prison Service play a crucial role in our community and any attack on them is an attack on all of us.
"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.
"We appeal to anyone with any information on this murder to contact the PSNI."
The Police Service of Northern Ireland (PSNI) chief constable Matt Baggott called for the public’s help. “This is an attack on all people and we need the full support of everyone,” said Baggott.
“Police will be increasing activity in a number of areas as a result of this murder but the most important thing is for people to remain calm, put their trust in police and work with us to catch the killers,” he added.