Paul Zinken / AFP – Getty Images  "We can not say anything about the motive of the attacker," said police spokesman Michae L Gassen.
Let our messages meet your inbox. The news and stories that mattered delivered weekdays morning.
The police later said that the man who was not a patient at the hospital had been questioned overnight. The police also investigated whether threats had been made by Weizsaecker or his family in the past.
The 59-year-old was the son of one of the most respected German presidents. Richard von Weizsäcker became the head of state of the Federal Republic of Germany in 1984, and when the country was incorporated, he became the first president of the new nation, which served until 1994. He died in 2015.
Fritz von Weizsäcker was one of four ex-presidential children. His sister Beatrice posted a picture of Jesus on the cross on Instagram after her brother was killed.
Christian Lindner, chairman of the Free Democratic Party, whose member Fritz von Weizsaecker was a member, was shocked by the murder.  "I am stunned and must share my grief," tweeted Lindner. "Once again, one wonders what kind of world we live in."
The board of the Berlin Charité Hospital said that they were "deeply shocked by the violent death of their highly respected friend and colleague." We are with his family and colleagues at the Schlosspark-Klinik. "
Von Weizsaecker studied and worked at several hospitals in Germany and abroad, including Harvard Medical School in Boston and a hospital in Zurich, where he specializes in internal medicine and gastroenterology.
On Tuesday evening he delivered a lecture on the increasingly common fatty liver disease was open to all and the local media reported that several colleagues were also in the audience.
Weizsaecker's assassination reflects a similar incident in 2016, when a man at the Benjamin Franklin Hospital in Berlin killed a doctor fatally
Weizsäcker's are one of Germany's best-known families, Richard von Weizsäcker was not only one of the most popular, but also one of the most respected presidents in the country.
In 1985, in a speech on the occasion of the 40th anniversary of the defeat of Germany, the then West German President von Weizsäcker called the "Liberation Day" the anniversary of the end of the war. His words were supported by most Germans, and to this day the speech is often cited by politicians and taught in schools.