(CNN) The son of Germany's ex-president Richard von Weizsäcker was stabbed to death while giving a lecture in Berlin on Tuesday night, local police have confirmed.

Fritz von Weizsäcker, a 59-year-old medical doctor, was delivering a lecture at the Schlosspark-Klinik hospital in the west Berlin district of Charlottenburg, a Berlin police spokesman told CNN.

At about 7p.m., a man approached von Weizsäcker in the lecture room and stabbed him with a knife. Despite efforts to save him, von Weizsäcker died at the scene. Police said a 57-year-old German man was arrested.

A 33-year-old off-duty police officer overwhelmed the attacker, allowing him to be taken into custody by police, authorities said.

In the course of intervening, however, the policeman was seriously injured and subsequently required medical treatment. His injuries were not thought to be life threatening.

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