In 1975, Klein participated in an attack on OPEC headquarters in Vienna organized by the international terrorist "Carlos the Jackal", in which he was seriously injured.
[3] His mother was imprisoned in Ravensbrück concentration camp for Rassenschande ("racial pollution") during World War II.
[3] He took part in the 1975 attack organized by Carlos the Jackal on an OPEC conference in Vienna, in which three people were killed and Klein himself shot in the stomach.
[12] Klein renounced terrorism in 1977, sending a letter to Der Spiegel (with his gun enclosed) in which he warned of planned RZ attacks on two leaders of the German Jewish community.
[13] Klein further explained his change of views in a 1978 interview with the French journalist Jean-Marcel Bouguereau [fr] and a 1979 book entitled Mercenary Death, for which Cohn-Bendit wrote the foreword.
[14] After spending two decades in hiding, mostly in France, in September 1998 he was apprehended in the Normandy village of Sainte-Honorine-la-Guillaume, where he had been living for five years.
[15] Joschka Fischer, then Germany's Foreign Minister, testified at his trial as a character witness; his presence intensified the controversy then playing out over his radical past.