An unnamed 22-year-old Danish man identified as the suspect was in custody following the incident at Fields shopping center, police confirmed via NBC News.
Authorities said the man is believed to have acted alone and targeted random victims, with no initial signs linked to organized terror.
The 22-year-old is scheduled to appear in court on Monday (July 4) and face a manslaughter charge, which would carry a possible life sentence in prison, according to police.
"My thoughts go to the wounded, relatives and others affected after this completely meaningless and terrible act," said Justice Minister Mattias Tesfaye in a news conference Monday via NBC News. "We do not yet know the motive behind it, but I can assure you that the authorities are making every effort to get to the bottom of this matter so that the person or persons responsible can be prosecuted."
Authorities have not released the names of the victims killed in the shooting, however, police inspector Søren Thomassen confirmed that the casualties include two 17-year-old Danes, one male and one female, and a 47-year-old Russian native who was living in Denmark, while providing an update during Monday's news conference.
The four critically injured victims include a 40-year-old and 19-year-old woman, both from Denmark, as well as a 50-year-old man and 16-year-old girl, both from Sweden, officials confirmed.