The man has not yet been identified, though a police spokesperson confirmed that he was pronounced dead at the scene. His body has been sent to the National Board of Forensic Medicine (RMV) building in Solna in an effort to identify it.
The car drove into the City Hall on the island of Kungsholmen and caught fire at around 2am.
The vehicle was first spotted by a police patrol further west on the island, and officers decided to carry out a check on it. However, the car disappeared from sight after police signalled for it to stop.
“When [the officers] came to the city hall, they saw the same car there, on fire,” said police spokesperson Towe Hägg.
“It is part of our job to check vehicles occasionally, but I don't know the circumstances that made them choose to do so in this case,” Hägg added.
The City Hall was cordoned off until around 3:30am. Police had still not been able to piece together the cause of the crash by Thursday evening, but are investigating it as a traffic fatality.
“We used dogs to search the area to see if there had been other people in the car, which there weren't,” said Hägg.
Staff with their offices in the affected part of the building were working from home on Thursday, with public tours of the City Hall suspended but expected to resume on Friday.
The deputy head of the City of Stockholm said that the car was likely driving at a high speed when the crash occurred.
“It knocked down one railing, passed between two trees, two pillars, and likely flown over two flower beds. You typically can't drive in that way if you aren't doing so at a very high speed,” Fredrik Jurdell told news agency TT.
Questions have been asked about security at the building following the incident, though Jurdell believes it was an accident:
“It's too early to say if we'll examine security just now, but we'll ask the question. We're aware of the reality that we live in a tricky world. But there's always a balance to be struck. How much should you reduce access for security's sake?”