What we know …

Four people were killed and at least 15 injured when a stolen truck slammed into a crowd of people outside a busy department store in central Stockholm, in what the prime minister described as a “terror attack.”

What happened?

The incident occurred just before 1300 GMT on Friday at the corner of the Ahlens department store and Drottninggatan, Stockholm’s biggest pedestrian street. “Police received a call from SOS Alarm that a person in a vehicle has injured other people on Drottninggatan,” police wrote on Twitter. Pictures showed a large blue truck with a mangled undercarriage smashed into the store.

Who was the attacker?

Prosecutors said police arrested a man “for a terrorist crime” early yesterday. Police later said they believed he was the driver.

Police had earlier said they had detained a man who “matched the description” of a suspect captured on video surveillance cameras near the scene of the attack. The image showed a man wearing a white sweater and dark hoodie under a military green jacket, with dark stubble.

Was it terrorism?

Swedish Prime Minister Stefan Lofven described the incident as a “terror attack”. “Sweden has been attacked. Everything points to a terror attack,” he said. In 2010, another section of Drottninggatan was the scene of Sweden’s only other terror attack, when a suicide bomber blew himself up, injuring several others.