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 7 p.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.
Police have since launched a murder investigation but a possible motive for the attack remains unclear. The suspect is due to appear before a magistrate Wednesday.
Von Weizsäcker specialized in internal medicine and gastroenterology.
He began his career as a resident at the University Medical Center at the University of Freiburg, and had studied and worked at a number of hospitals overseas including Harvard Medical School in Boston and the University Hospital of Zurich.
Since 2005, he had held the position of chief physician of the department of internal medicine at Schlosspark-Klinik.
He was one of the former president’s four children.
Richard von Weizsäcker held the largely ceremonial position of president between 1984 and 1990 and was in post during the fall of the Berlin Wall and Germany’s reunification.
One of the country’s most respected heads of state, he is remembered for his thoughtful speeches, including an address in 1985 when he warned against forgetting Germany’s past in a speech marking the 40th anniversary of the end of World War II.