Police and forensic officers examine the scene of a fatal shooting of a Northern Ireland prison officer on the M1 motorway near Lurgan, Northern Ireland, on Thursday. He was killed in an ambush as he was driving to work. (Associated Press)

Police and forensic officers examine the scene of a fatal shooting of a Northern Ireland prison officer on the M1 motorway near Lurgan, Northern Ireland, on Thursday. He was killed in an ambush as he was driving to work. (Associated Press)