A 38-year-old was critically injured in an attack in Dortmund.
The police announced on Friday that the man was hit in the head with an object.
A suspect was provisionally arrested, said the responsible public prosecutor Felix Giesenregen.
However, there is no urgent suspicion.
Dortmund - According to the announcement, the dispute occurred late Monday evening in Dortmund's northern city.
In the course of the dispute, in which two people are said to have been involved, the 38-year-old was attacked.
One possible motive is relationship reasons, said Giesenregen.
"But an unknown third party cannot be excluded either."
The Dortmund police are investigating suspicion of an attempted homicide, it said.
The officers set up a homicide squad, they are looking for witnesses.
dpa
