At least one scumcrumpet has been taken into custody, according to Prime Minister Stefan Lofven.
"Sweden has been attacked," Lofven said. "This indicates that it is an act of terror."
While no shouts of "Allahu akbar" have been reported, this type of indiscriminate killing has all the butt-marks of an Islamic terror attack, although there was no immediate claim of responsibility.
Police said a truck ran through a crowd at Ahlens Department Store, injuring "a large number of people." The central train station in Stockholm has been evacuated, whether by precautions or otherwise, is still unknown.
SVT, the Swedish media, said that at least five people have been killed but police couldn't immediately confirm that number. Other reports said that at least two people were killed, but as is typical of a breaking story, these numbers will be adjusted.
There were also reports that shots were fired in other parts of the city, but spokeswoman Towe Hagg could not confirm this.
Photos on scene showed a beer truck sticking out of a department store. Aftonbladet Daily reported that Swedish beer maker Spendrups said one of its trucks had been carjacked early Friday.
"During a delivery to the restaurant Caliente, someone jumped into the driver's cabin and drove off with the car, while the driver unloads," communication director Marten Lyth told TT news agency.
Homeland Security officials are monitoring the situation in Sweden.
"We stood inside a shoe store and heard something . . . and then people started to scream," witness Jan Granroth told Aftonbladet Daily. "I looked out of the store and saw a big truck."
Swedish news agency TT said that several people were rushed away in ambulances and live footage showed smoke pouring out of the department store that was smashed into by the truck.