German police are investigating the death of doctor Fritz von Weizsiker, son of former German President Richard von Weizsiker, who was stabbed Tuesday night while delivering a lecture at a Berlin hospital.

Police said on Wednesday that a 57-year-old man was suspected of carrying out the murder.

Police said the suspect was a German and had not been known to police before. He is due to appear before the investigating judge later today.

Police gave no further details on the identity of the man or the motive for the crime.

Chief medical officer Fritz, 59, was giving a medical lecture at the Schlosspark hospital in Berlin when a man rushed to the crowd just before 7 pm (local time) and stabbed him with a knife, a police spokeswoman said. No medical relief.

The suspect was arrested at the crime scene. Authorities are investigating in all directions.

According to the spokesperson's statements, the authorities are asking the family of Von Weizsiker if there were threats.

According to police data, many among the audience, who numbered about 20, helped to arrest the culprit. One individual, a policeman who was present in the lecture in his private capacity, was injured.

Fritz von Weizsiker left a long career as a doctor, working in Freiburg, Boston and Zurich, and has been chief of physicians at the Department of Internal Medicine at the Schlosspark Berlin since 2005.

The victim's father, Richard von Weizsiker (1920 - 2015), was Germany's president from 1984 to 1994, and was previously mayor of Berlin.