The first alarm came to police shortly after 6pm when shots were fired in Sollentuna, a suburb north of the city centre.
The two victims, aged 20 and 25, were taken to hospital with life-threatening injuries, police said, and the 20-year-old died later in the evening. The condition of the other man was described as “serious but stable”.
The approximate locations of the three shootings.
About an hour after the first shooting, a man was shot and wounded in the leg in Kallhäll, about ten kilometres away from Sollentuna.
Police were then called out to Blackeberg shortly before 11pm after receiving multiple reports of a shooting. Police later said that the victim in Blackeberg had died, and that they had opened a preliminary investigation into murder. A dog was also injured in the shooting, police confirmed.
“I heard seven to ten shots, then came the air ambulance, six police cars and at least four ambulances,” one witness told the Aftonbladet daily.
One person is being held on suspicion of murder, in connection with the Blackeberg shooting.
Police brought in extra resources during the night to work with technical investigations at the three crime scenes, and to offer additional security for local residents. They have also appealed to the public for any tips or information relating to the shootings.
“Of course we are looking at whether there is a link between the events . I cannot confirm or dismiss it right now, but it's being looked into,” police press spokesperson Anna Westberg told local paper Mitt i Stockholm.