The man is suspected on probable grounds of aiding and abetting murder and attempted murder. The prosecutor will decide whether to request detention or release the man by 12 noon on Thursday.
The man was not near the school during the attack, says Tobias Ahlén Svalbro, press spokesperson for the Central Police Region.
We believe that he has no connection to the school and that he was not present at the incident itself.
According to information provided to Aftonbladet, the police suspected early on that another person may have been involved in the attack. This weekend, the police, according to the newspaper's sources, carried out a raid in the Stockholm area and arrested a person suspected of involvement.
The police do not provide details about where the man was arrested but confirm that it was not in Fagersta.
An 18-year-old man has previously been arrested for murder and attempted murder. A 17-year-old girl was killed and three teenage boys were injured in the school shooting on Friday.
