LONDON (AP) — A former British paratrooper was found not guilty Thursday on murder charges relating to the 1972 Bloody Sunday massacre in Northern Ireland that saw 13 people killed in a flurry of bullets.

Judge Patrick Lynch ruled at Belfast Crown Court that prosecutors failed to prove that the veteran identified only as “Soldier F” had opened fire, with intent to kill, on unarmed civilians who were running to safety.

Soldier F was the only soldier ever charged in connection with the events on Jan. 20, 1972 in Londonderry, also known as Derry. It was one of the deadliest incidents of the period known as “The Troubles," the conflict between mainly Catholic supporters of a united Ireland and predominantly Protestant forces who wanted Northern Ireland to remain part of the United Kingdom.

In addition to the 13 killed, 15 others were wounded on Bloody Sunday. Survivors have spoken of the confusion, chaos and terror as soldiers opened fire and bodies began falling after a large civil rights march through the city.

While the sectarian violence largely ended with the 1998 Good Friday peace accord and Northern Ireland has become a beacon of hope for other conflicts around the world, tensions remain.

Soldier F was shrouded from view in court by a curtain throughout the five-week trial, and did not testify in his defense. It was a nonjury trial, as has been the standard in cases involving cases related to the decades-long period of sectarian violence in Northern Ireland.

He had pleaded not guilty to two counts of murder for the deaths of James Wray, 22, and William McKinney, 27, and five counts of attempted murder for the shootings of Joseph Friel, Michael Quinn, Joe Mahon, Patrick O’Donnell, and for opening fire at fleeing demonstrators.

The judge said the evidence presented against the veteran fell well short of what was required for conviction. But he berated the soldiers from the Parachute Regiment on duty that day for the way they responded, and how their actions sullied the memory of a unit that had a proud record in World War II.

“They had totally lost all sense of military discipline," he said. “Shooting in the back unarmed civilians fleeing from them on the streets of a British city. Those responsible should hang their heads in shame.”

However, the judge said that because there was no concept of “collective guilt” in the courts, he wasn't able to issue a guilty ruling against Soldier F.

The sole evidence against Soldier F was from two other veterans, Soldiers G and H, one of whom is deceased while the other refused to take to the dock for fear of incriminating himself.

“Their statements, the sole and decisive evidence, cannot be tested in a way that witnesses giving evidence from the witness box would be," the judge said. “Delay has, in my view, seriously hampered the capacity of the defense to test the veracity and accuracy of the hearsay statements."

The verdict was a blow to families of victims who have spent more than a half-century seeking justice.

Mickey McKinney, brother of William McKinney who was shot dead on Bloody Sunday, said the failure to bring anyone to justice “lies with the British state" for failing to investigate the murders "properly, or indeed at all; and with the British Army who shielded and enabled its soldiers to continue to murder with impunity.”

Over the decades since, Bloody Sunday has become a source of shame for a British government that had initially claimed that members of a parachute regiment fired in self-defense after being attacked by gunmen and others hurling firebombs.

Supporters of army veterans complain that their losses have been downplayed and that they have been unfairly targeted in investigations.

Defense lawyer Mark Mulholland attacked the prosecution's case as “fundamentally flawed and weak” for relying on soldiers he dubbed “fabricators and liars,” and the fading memories of survivors who scrambled to avoid live gunfire that some mistakenly thought were rounds of rubber bullets.

Veterans and their campaigners welcomed Thursday's verdict.

“It has become increasingly clear that the admissibility of certain types of evidence, particularly those based on decades-old recollections, remains deeply problematic," said Northern Ireland veterans commissioner David Johnstone.

“Soldier F has faced legal scrutiny in various forms for more than a quarter of a century, and it is my hope that today’s ruling by Judge Lynch brings that long and arduous process to a close,” he added.

Prosecutors had argued that the soldiers, without justification, had all opened fire, intending to kill, and thus shared responsibility for the casualties.

A formal inquiry cleared the troops of responsibility, but a subsequent and lengthier review in 2010 found soldiers shot unarmed civilians fleeing and then lied in a cover-up that lasted for decades.

Then Prime Minister David Cameron apologized and said that the killings were “unjustified and unjustifiable.”

The 2010 findings cleared the way for the eventual prosecution of Soldier F, though delays and setbacks kept it from coming to trial until last month.