The arrested man was found in a residence, which is now blocked off, in the town of Harmånger.
We are working with various investigative measures to secure tracks, says the police's press spokesperson Maria Hall.
According to the police, a sharp object was used in the assault.
The man was detained after an interrogation at 7 pm, on probable cause suspected of murder, states the Prosecution Authority in a press release.
Convicted of assault
The man has recently been sentenced to probation and community service for assaulting a person and threatening them with a knife, reports Sveriges Radio Ekot.
The ambulance was alerted to the scene to help the now murder-suspected man, states the prosecutor to Ekot.
The police responded with a large number of resources. Residents on the scene were urged to stay indoors during the operation.
The alarm came in at 11:30 on Saturday morning. According to the region's deputy health and medical care director Susanna Björklund, the ambulance had responded to a prio 3 mission, i.e. an alarm of lower priority.
Police and rescue services were quickly on the scene, but unfortunately, the person's life could not be saved, she says.
Region in crisis mode
The region has gone into crisis mode due to the incident and is working with crisis support for affected employees and relatives.
We have an employee who is in shock, says Susanna Björklund.
I have worked for many years in the healthcare system and I have never been involved in such an incident.
Neighboring regions are helping to secure staffing as needed.
