The son of former German President Richard von Weizsäcker has been stabbed to death at a Berlin hospital.
Doctor Fritz von Weizsäcker, 59, had just given a lecture on liver diseases.
His father served as president during the reunification of Germany in 1990.
The suspect, also in his 50s, is in police custody. The motive for the attack was not immediately clear. An off-duty policeman was seriously injured when he stepped in to overpower the attacker.
Despite efforts to save Mr von Weizsäcker, he died at the scene.
The attack occurred at the Schlosspark hospital in western Berlin neighbourhood of Charlottenburg, where he worked as a doctor.
The policeman, who happened to be in the audience, was one of a number of people who intervened. He was taken to another hospital to be treated for his injuries.
Richard von Weizsäcker served as president of West Germany from 1984 to 1990. He was in post during the reunification of West and East Germany, continuing to serve as president of a united Germany until 1994. He died in 2015.
Christian Lindner, head of the liberal Free Democratic Party said on Twitter that he was “stunned” by the death of his friend, adding that “once again we ask ourselves what sort of world we are living in.”__BBC