Police have begun a preliminary investigation into the suspected murder and attempted murder.
The two youngsters, both in their teens, were alone in the house on Wednesday evening, when the dramatic events apparently unfolded.
Marie-Louise Nilsson, station officer at the Västerort police force, told news agency TT that police are still unsure if there are any signs of a break-in.
“We’ll have to wait and see what the technicians find,” she concluded.
A relative found the young man dead in the house around midnight, and the woman severely injured. She was immediately taken to Karolinska University Hospital in Solna, outside Stockholm.
In order to better understand how this event unfolded, the police are hoping to be able to question the woman. However, it may be some time before this is possible, as she is currently held sedated for medical reasons.
No one has been arrested for the crime yet.
Today police investigators continue their interrogations, door-knocking and technical investigations.
“Then we’ll see what we’ve found out,” Mikael Säter, deputy station officer at the Västerort police force, said to TT.
He also stated that he did not know if the man and woman were known to the police for earlier criminal activity.