After using an axe to break down the door, the man stabbed both his 27-year-old ex-girlfriend and his sister, who happened to be visiting at the time, police said on Wednesday.
The suspect is father to two children who were also in the apartment along with a male visitor. He threatened to kill everyone in the apartment because he wasn't allowed to see the children. When the male visitor brought the children to safety, the suspect stabbed the two women.
The 37-year-old man's ex-girlfriend died shortly thereafter in the hospital. According to police, his sister's wounds are not life threatening, though she remains hospitalized.
The fleeing suspect resisted arrest and was subdued with a bite from a police dog, officials said. He has refused to discuss the incident with police in the German state of Lower Saxony.
The man's violent behavior had already aroused concern in February, and he was under a police restraining order not to go near the woman's apartment. Family members are receiving psychological care, police said.