The son of the former German president Richard von Weizsäcker died after being stabbed by unknown assailants at a hospital in Berlin.
The authorities said 59-year-old Dr Fritz von Weizsäcker had just finished giving a lecture on liver diseases when the incident happened. Richard von Weizsäcker served as the German president in 1990.
An off-duty policeman was seriously injured after stepping in to apprehend the attacker. The unidentified officer is in stable condition after coming out of surgery.
The suspect, a 57-year-old man, was later arrested and admitted to a psychiatric unit. Prosecutors believed the attacker suffers from mental illness but his motive was not immediately established.
The authorities said the man travelled from the south-western state of Rhineland-Palatinate to Berlin by train to carry out the attack.
The police searched the suspect’s apartment located in the town of Andernach.