LONDONDERRY: The Northern Irish city of Londonderry began commemorations Sunday of one of the darkest days in modern UK history when, 50 years ago, British troops without provocation killed 13 unarmed civil rights protesters.

The anniversary of “Bloody Sunday” comes with Northern Ireland’s fragile peace destabilised by Brexit, and with families of the victims despondent over whether the soldiers involved will ever face trial.

The 13 demonstrators died on January 30, 1972, when members of the British Parachute Regiment fired more than 100 high-velocity rounds into crowds in Londonderry, known as Derry to pro-Irish nationalists. Some of the victims were shot in the back, or while on the ground, or while waving white handkerchiefs as the shots ripped through narrow streets and across open wasteland in the Catholic Bogside district.

On Sunday, several hundred people including relatives of the victims retraced the fateful 1972 march that preceded the tragedy, walking in sombre silence under a leaden grey sky.