During the investigation, the suspicions have been strengthened and the boy is now requested to be detained.
Prosecutor Maria Edström submitted her arrest petition at lunchtime on Wednesday.
- The arrest concerns a serious weapon crime and murder, says Maria Edström.
The degree of suspicion has been raised for probable cause, which is the higher degree of suspicion.
She does not want to comment on what lies behind the strengthened suspicions.
The arrest hearing will take place in Eskilstuna tomorrow Thursday, the Public Prosecutor's Office writes on its website.