Swedish newspaper Dagens Nyheter reported that the incident occurred on Wednesday night at a clinic in Västerås. It's believed the man escaped from his secure unit in the clinic and headed for another department.
Whilst there he became aggressive towards staff and threatened them with a razor blade. Security guards attempted to calm the man down but their efforts were unsuccessful. Police were called to the scene.
The newspaper added the man became quite aggressive and that the police wore body armour and used pepper spray to protect themselves.
When the situation calmed down the man was transferred into a secure hospital bed with straps. However, he wasn't breathing and attempts to resuscitate him were unsuccessful.
The man was subsequently declared to be deceased but the exact cause of his death remains unknown.
The Västmanland police have so far declined to go into detail about the specific incidents leading up to the man's death. It's understood that the police's internal investigation department has opened a preliminary investigation of misconduct.