Swedish prosecutors on Saturday confirmed media reports that they have a 39-year-old man from Uzbekistan in custody for Friday’s truck attack that left four dead. Anders Thornberg, head of the Swedish Security Service, said the man was known to police. Saying that “the suspect didn't appear in our recent files but he earlier has been in our files,” Thornberg didn’t elaborate on why the man was on authorities’ radar. Dan Eliason, the head of Sweden's National Police, said earlier that the suspect in custody is believed to have been the driver in the attack, which saw a beer truck hijacked and driven into a crowd in Stockholm on Friday. In addition to the four killed, another 15 were injured. Eliason also said police found an object that “could be a bomb or an incendiary object” in the truck. Earlier, a police spokesperson said police had not yet excluded the possibility that the man had accomplices. The hijacked beer truck plowed into a crowded area of the city and ultimately rammed into a department store on Friday, with the driver escaping in the ensuing frenzy. No group has come forward to claim responsibility for what authorities say was a terrorist attack. The attack was reminiscent of similar attacks using hijacked vehicles in Nice, Berlin and London, all of which were claimed by the Islamic State.