A murder investigation is to be launched into the killings of 13 Roman Catholic civil rights marchers by British soldiers in Londonderry 40 years ago, Northern Ireland's police service say.
The announcement came a week after Britain's Queen Elizabeth for the first time shook the hand of former Irish Republican Army (IRA) guerrilla commander Martin McGuinness, who was there on the day, helping draw a line under a conflict that cost the lives of thousands of soldiers and civilians.
The decision by the Police Service of Northern Ireland to look into possible murder charges was taken after review of a report published two years ago, which said the civilians shot dead at the height of Northern Ireland's sectarian "Troubles" were innocent and had posed no threat to the military.
"It is a matter that I think we should be investigating and will be investigating," chief Constable Matt Baggott said at a press conference in Belfast.
The Saville Report was published after a 12-year public inquiry by British High Court judge Lord Saville, which reversed the findings of a swift inquiry carried out by another judge, Lord Widgery, immediately after Bloody Sunday and which said soldiers only opened fire after being fired upon.
The Widgery report had long been branded a "whitewash" by the families of those killed.
The victims' families, who have campaigned for full exposure and accountability for the events on that day, welcomed the announcement and said it was a decision they had been expecting.
"After hearing what we heard today it's a step in the right direction because, myself, my family and most of the families (of those killed) want prosecutions," said John Kelly, whose brother Michael was shot dead on Bloody Sunday.
The killings changed the course of the violent "Troubles" that erupted in Northern Ireland in the late 1960s.
The conflict pitted nationalists, mostly Catholics, who wanted the province to secede and become part of the Republic of Ireland, against Unionists, mostly Protestants, who wanted it to remain part of the United Kingdom.
On Sunday, January 30, 1972, British troops opened fire during an unauthorised march in the Bogside, a nationalist area of Londonderry. They killed 13 people and wounded 14 others, one of whom died later. The victims were all unarmed Catholics.
The Saville report, which cost 195 million pounds (NZ$377 million), said the first shots were fired "possibly in panic or fear" and other soldiers reacted to the sound of gunfire "by losing their self-control and firing".
The killings drove hundreds of new volunteers into the illegal IRA armed group, which stepped up its campaign of bombings and shootings in Northern Ireland and the British mainland. It was not until 1998 that the Good Friday peace deal was brokered after more than 3600 had died.
British Prime Minister David Cameron issued an apology for Bloody Sunday over two years ago following the Saville report publication and said the deaths were "unjustified and unjustifiable".
A senior officer said the police investigation would take four years and involve 30 detectives but it had not yet been established when the police investigation would get under way due to the huge deployment of officers needed.