Swedish authorities confirmed Saturday that the suspect in a deadly truck attack in central Stockholm is a 39-year-old native of Uzbekistan who appeared in past intelligence files.
Authorities also told reporters they are trying to determine whether a "technical device" found in the driver's seat of the stolen vehicle is an explosive.
National Police commissioner Dan Eliasson told reporters that investigators could not rule out further accomplices in the attack, but said they were convinced that the suspect in custody was the man who drove the vehicle that plowed into bystanders on a pedestrian walkway Friday before slamming into a department store, killing at least four people and injuring 15 others.
"There is nothing to indicate that we've got the wrong man," Eliasson said. "On the contrary, the suspicions have strengthened."
Prosecutors said the suspect was being held for "terrorist offenses by murder” and would face a pre-trial custody hearing before midday Tuesday or be released.
There was no immediate claim of responsibility for the attack.
Prime Minister Stefan Lofven, who said the attack left Sweden in a state of shock, urged citizens to “get through this.” On Saturday, he walked through the streets of the capital, chatting with residents. Swedish flags flew at half-staff throughout the city.
Visiting the site of the attack at the upscale Athlens department store, Sweden’s Crown Princess Victoria laid roses on the ground and wiped away a tear. “We must show a huge force, we must go against this,” she told reporters.
The attacker commandeered a beer truck and drove at high speed for some 500 yards down the Drottninggatan — a main pedestrian street in the city center — hitting bystanders before slamming the vehicle into the department store. At that point, the vehicle caught fire and the driver fled.
"People were screaming and running in all directions,” said Brandon Sekitto, who was in his car nearby. “(The truck) drove straight into the Ahlens entrance.”
“I saw the driver, a man in black who was light around the face,” Sekitto told the Swedish daily Dagens Nyheter. “Some women were screaming, ‘Run! Run!’”
The suspect was arrested several hours later, after making his way around the city by metro, bus and on foot. Wearing a hooded green jacket, he was shown in a police photo on an escalator at a nearby subway stop.
Aftonbladet reported at least two witnesses recognized the suspect from the police photo and and alerted authorities. One witness followed him by car at one point until police arrived.
Bystanders described the man, who had pieces of glass on his clothing, as nervous and erratic.
The newspaper Dagens Nyheter said the suspect sought asylum in Sweden several years ago but did not have a criminal record. It quoted a woman who owned the apartment where the suspect is registered as saying he is a construction worker with wife and children still living abroad. She described him as showing no signs of extreme religious fanaticism.
Anders Thornberg, head of Sweden’s domestic intelligence agency, acknowledged the suspect "appeared in our intelligence gatherings in the past."
Prosecutor Hans Ihrman told reporters the suspect has not yet spoken to authorities and could not confirm whether he was a legal resident of Sweden. He said investigators were "trying to profile him and his behavior" and were not yet ready to identify him publicly.
Eliasson, the police commissioner, described the suspect as “a more marginal character.” He said authorities were screening the his phone calls, social media activity, contacts and links to try to find how the attack unfolded and whether he was acting alone.
"We do not know whether there are other persons involved in this act or not," he said, "but we are not excluding that."
Contributing: Associated Press.