A former British soldier was charged with murder on Thursday over the 1972 Bloody Sunday killings, one of the darkest chapters in the Northern Ireland conflict. The ex-paratrooper, identified only as Soldier F, was charged with murdering two people and the attempted murder of four others in what was an early turning point in the history of the Troubles, three decades of deadly sectarian unrest. British troops opened fire on a civil rights demonstration in Derry, Northern Ireland's second city, killing 13 people on January 30, 1972. A 14th victim later died of his wounds. Soldier F was one of 17 British veterans who had faced investigation, plus two alleged Irish Republican Army (IRA) paramilitaries, but he was the only one charged. Relatives of the victims looked visibly upset after learning that there would only be a prosecution over two of the deaths. "The Bloody Sunday families are not finished yet," said John Kelly, whose 17-year-old brother Michael was killed. He raised the prospect of a legal challenge against the decisions not to prosecute others. "We have walked a long journey since our fathers and brothers were brutally slaughtered on the streets of Derry on Bloody Sunday," he said. "The dead cannot cry out for justice; it is the duty of the living to do so for them." - 47 years to criminal charges - A 12-year public inquiry -- the biggest investigation in UK legal history -- concluded in 2010 that British paratroopers lost control and that none of the casualties had been posing a threat of causing death or serious injury. Police then launched a criminal investigation and handed files to Northern Ireland's Public Prosecution Service state prosecutors in November 2016. PPS director Stephen Herron announced the charging decisions on Thursday. The relatives of those killed walked together from a memorial in Derry to hear the prosecutors' decision first in private. Herron said: "There is sufficient available evidence to prosecute one former soldier, Soldier F, for the murder of James Wray and William McKinney," and the attempted murders of four others. "In respect of the other 18 suspects, including 16 former soldiers and two alleged Official IRA members, it has been concluded that the available evidence is insufficient to provide a reasonable prospect of conviction." Bloody Sunday remains a hugely politically sensitive incident. The British Parachute Regiment opening fire on a civil rights march in the majority Catholic area of the Bogside in Derry helped galvanise support for the Provisional IRA early in the Troubles. A photograph of a Catholic priest waving a bloodstained handkerchief as he tried to help 17-year-old victim Jackie Duddy to safety became a defining image of the incident. - Indebted to soldiers: Williamson - British Defence Secretary Gavin Williamson said the defence ministry would provide Soldier F with full legal and welfare support. "We are indebted to those soldiers who served with courage and distinction to bring peace to Northern Ireland," he said. "Our serving and former personnel cannot live in constant fear of prosecution." The decision infuriated some former British troops who were sent on active duty in Northern Ireland. "It's one soldier too many as far as we're concerned," said Alan Barry, 54, who founded the Justice for Northern Ireland Veterans group. "It's all about appeasement... and if that means throwing one or two veterans under a bus then that's what they'll do." Following the public inquiry's findings in 2010, Britain's then-prime minister David Cameron issued a formal state apology for the killings, calling them "unjustified and unjustifiable". Explaining the decisions, PPS director Herron said much of the material available to the inquiry was not admissible in criminal proceedings. A decision not to prosecute "in no way diminishes any finding by the Bloody Sunday Inquiry", he explained. Jackie Duddy's brother said the room "just went silent" when the relatives were told of the decision. "It was like getting stabbed in the back again." Mickey McKinney, whose brother William, aged 27, was shot in the back, stressed: "Justice for one family is justice for all of us." The Irish government said that all victims' families deserved "access to effective investigations into killings" and "the opportunity to find justice... regardless of the perpetrator." Linda Nash (R), who lost her brother William on Bloody Sunday, is comforted outside the City Hotel in Derry. In 2010, the then British prime minister David Cameron issued a formal state apology for the Bloody Sunday killings Relatives and supporters of the victims of the 1972 Bloody Sunday killings hold images of those who died as they march from the Bogside area of Derry. Julieann Campbell, the niece of Bloody Sunday victim Jackie Duddy, poses for a photograph by a mural depicting the late Bishop Edward Daly waving a white handkerchief as Jackie Duddy is carried away during the 1972 Bloody Sunday killings. Northern Ireland's Director of Public Prosecutions Stephen Herron.