Police received a call just after midnight to say that a woman was lying dead in her apartment in Vårby.
“She had received injuries from some sharp object, possibly a knife. The incident probably occurred on Tuesday afternoon,” said police spokesman Mats Nylén.
The 58-year-old man who had called the police was still in the apartment when police arrived.
“The suspect has made certain concessions,” said criminal investigator Lars Lundin.
The nurse had a purely professional relationship to the suspect. She went to his apartment after work on Tuesday because she was worried about his condition.
The two had known each other for many years.
The man lived in an apartment attached to a non-institutional care home.
Detention proceedings are to be held on Thursday.