Police in Stockholm have confirmed Chris Bevington, a 41-year-old British national, was among those killed in a lorry attack in the Swedish capital on Friday.
Three others also died - one Belgian and two Swedes - and 15 others injured, many seriously.
Here is what is known so far on the attack and the police investigation:
The lorry was driven along Drottninggatan, a pedestrianised street in a busy Stockholm shopping district, before crashing into Ahlens department store just before 3pm local time.
Swedish beer maker Spendrups said one of its trucks had been hijacked earlier on Friday. The lorry driver reportedly tried to fight off the hijacker.
How many people were hurt?
Four people were killed and at least 15 others were injured in the attack.
Among those who died was Chris Bevington, a 41-year-old British national.
In a statement, his father, John Bevington, said: "We are all devastated by the untimely and tragic death of our talented, compassionate and caring son Chris.
"A wonderful husband, son, father, brother and close friend to many. The family requests absolute privacy at this incredibly difficult time to mourn his passing in peace."
Sweden's health service said on Saturday that 10 victims remained in hospital.
Four were said to be seriously injured and two are in intensive care.
The one remaining child still in hospital is not seriously injured.
Who has been arrested?
Soon after the attack police in Stockholm released a photo of a suspect. A short time later, a man matching his description was detained.
On Saturday, police confirmed the suspect is a 39-year-old man from Uzbekistan. His name was later confirmed by court documents as Rakhmat Akilov.
He is being held under an extended arrest "on suspicion of terrorist crimes through murder", the office of the Swedish prosecutor has said.
It is the strongest degree of suspicion in Sweden's legal system, which can apply several different levels to hold a person.
He was identified as a man police were "particularly interested in" after being arrested "in the vicinity" of the crash site, Stockholm police's Jan Evensson confirmed.
Evensson added that the man was spotted by a police patrol in Marsta, a northern Stockholm suburb close to the city's international airport, and was in a police photo released earlier Friday wearing a greenish hood at the top of an escalator.
Was the crash a terror attack?
Sweden's Prime Minister Stefan Lofven said all the evidence suggests the crash was a terror attack.
"Sweden has been attacked," he said in a televised press conference. "This indicates that it is an act of terror."
He added: "The country is in a state of shock. The aim of terrorism is to undermine democracy. But such a goal will never be achieved in Sweden."
Stefan Hector of Sweden's national police confirmed the crash was being treated as an "act of terror".
What has happened to the lorry?
The lorry used in the attack has been towed away from the central shopping street.
Police said cordons around the crime scene would remain in place until the on-site investigation has been completed.
Beauty products remain on display yards from where the department store shop window was smashed in, giving little clue to the carnage witnessed hours earlier.
What has the reaction been from around the world?
A host of world leaders have offered their condolences following the crash.
European Commission President Jean-Claude Juncker said "an attack on any of our [the EU] Member States is an attack on us all".
While Sweden's King Carl XVI Gustaf said his thoughts go "out to those that were affected, and to their families".
Downing Street confirmed Theresa May spoke with her Swedish counterpart Stefan Lofven and expressed condolences on behalf of the British people.