A 14-year-old girl was killed in a violent act in Central Franconia on Friday.
The police arrested the three-year-old brother of the teenager as a suspect.
The 41-year-old mother suffered serious injuries and was taken to a hospital, a police spokesman said.
On the morning of Epiphany, the police received an emergency call from Weisendorf (Erlangen-Höchstadt district).
It was initially unclear who had dropped him off.
The officers were able to provisionally arrest the 17-year-old brother "near the scene of the crime".
According to the first impression, the girl died from a "pointed, sharp object".
The crime took place in a semi-detached house in a residential area.
According to initial findings, the forty-one-year-old lived there with the 14-year-old girl and the seventeen-year-old.
Weisendorf is near Erlangen and has about 6800 inhabitants.