The Literature student Benno Ohnesorg became a martyr for West Germany's radical left when he was shot by a policeman in 1967. For those who looked over the Berlin Wall to East Germany as the epitome of good governance, the killing symbolised everything that was wrong with their country – corruption, self-complacency and an inability to deal with the crimes of the Nazis.
Some called it the "shot that changed the republic" and it would end up being used to justify the violent campaigns waged by leftist radical groups like the Baader-Meinhof.
But now history faces a major rewrite. The policeman who fired the fatal shot was not the typical West German policeman and fascist villain the left loved to hate, but was in fact working as a spy for the Stasi, East Germany's secret police force.
The evidence is presented in today's edition of the academic journal Deutschland Archiv, a result of lengthy research by historians Helmut Müller-Enbergs and Cornelia Jabs.
Sifting through the 120 miles of yellowing paper that make up the Stasi files in Berlin – files which its shredders and furnaces were unable to destroy as East Germany began its rapid slide into oblivion 20 years ago – the documents show the gunman Karl-Heinz Kurras began working with the agency in 1955.
As a result of the new information, criminal charges have once again been filed against Mr Kurras, who was acquitted in two previous criminal trials of negligent homicide.
But more than just being another criminal process against an ageing man, the discovery that a Stasi agent was the killer has caused an earthquake in the national psyche, especially among those who still cling to some of the ideals and policies of the GDR.
"I would never, never, ever have thought that this could be true," said Stefan Aust, a former editor-in-chief of the German news magazine Der Spiegel. The left would be doing a lot of reflective thinking in the weeks ahead, he said.
Murder and mayhem was committed in Mr Ohnesorg's name. Ulrike Meinhof, one half of the terrorist duo whose exploits were chronicled in the feature film The Baader-Meinhof Complex last year, mentioned Mr Ohnesorg's death when announcing the formation of the Red Army Faction in the autumn of 1967.
Now the fading Stasi files – which have managed to wrench apart old friendships, families and alliances long after the state which produced them went out of business – prove that Mr Kurras's paymasters in the East thought highly of him and gave him the cover name of Otto Bohl; a common practice at the time.
In an interview with the German daily Bild, Kurras, now 81, confirmed that he had been in the East German Communist Party. "Should I be ashamed of that or something?" he said. Asked about his connection with the Stasi, he replied: "And what if I did work for them? What does it matter? It doesn't change anything." He went on to say that the shooting of Mr Ohnesorg was an accident and that he received no money for his Stasi activities. "Other agents must have put those details in the file and been lining their own pockets with the money I supposedly got," he said.
Mr Ohnesorg had been taking part in a demonstration at West Berlin's opera house on 2 June, 1967, to protest the attendance of the Shah of Iran, Mohammad Reza Pahlavi. Pro-Shah demonstrators were flown in from Tehran to battle with the student protesters. In the violence that followed, a single shot to the head ended the life of the literature student at 8.30pm.
Straight after the killing, Mr Kurras received a Stasi communique ordering him to destroy his records and "cease activities for the moment".
The agent responded: "I need money for a lawyer".