It was on December 28 that double shootings occurred at two nearby addresses in Gubbängen in southern Stockholm.
In the latter case, it involved a shooting at a door in an apartment.
No one was injured in the shootings.
The police arrested two teenage boys the same evening, of which a 15-year-old boy was later detained on suspicion of attempted murder and aggravated weapons offences.
An automatic weapon found nearby was also seized.
Now another 15-year-old has been requested to be detained, suspected of the same crime.
The two 15-year-olds are suspected of involvement in both thefts.
Arrest hearings are held in Södertörn district court on Thursday.