Dutch prosecutors investigating the murder of three people on a tram say a letter was found in the gunman’s getaway car and it is one of the reasons why a terrorist motive is being seriously considered.
Three people were killed and three others seriously wounded in the attack in the central city of Utrecht.
Turkish-born suspect Gokmen Tanis was detained on Monday evening.
No connection has been found between him and the victims.
Prosecutors say a firearm was found when Tanis was detained.
“So far a terrorist motive is being seriously taken into account. Among other things a letter found in the getaway car and the nature of the facts give rise to that,” a statement said (in Dutch), without detailing the contents of the letter.
Other motives have not been ruled out.
Neighbours had earlier described the suspect as a “loser” and a petty criminal rather than a terrorist.
Reports said he had been involved in several court cases.
Who are the victims?
Two other suspects are in custody, aged 23 and 27, and authorities are assessing if they had any involvement in the attack. Their lawyer told Dutch media the men were brothers but not related to the main suspect.
The mayor of Utrecht confirmed that a 19-year-old woman who worked in a snack-bar and a 49-year-old youth coach from a sports club were among the dead. The third victim is described as a 28-year-old man.
The Desto club in Utrecht issued a statement saying all their thoughts were with the trainer’s wife and three children.
Three of the wounded are in a serious condition and Mayor Jan van Zanen said he was aiming to meet the victims’ families later. Two are women in their early twenties and a man in his seventies.
Flags were flying at half-mast on public buildings in the Netherlands on Tuesday and flowers were laid at the site of the attack in Utrecht’s 24 Oktoberplein.
At the scene
Anna Holligan, BBC News, Utrecht
Sarah cycled to the scene to lay a fresh bouquet of tulips, her 13-month-old toddler, Jet, harnessed in a seat on the front of the bike.
“I felt afraid to come out,” she told me. “But I had to show my daughter that we have to be strong, to keep living.”
A note pinned to a bunch of roses read, “It hit right through the heart.”
The victims appear to have been targeted at random. Among the tears and shows of solidarity, the overwhelming sense among the people is, it could have been one of us.
What is known about the suspect?
Police released Gokmen Tanis’s name after the shooting, as they searched his home and other addresses.
Prosecutors said he was known to police while friends told Dutch media that he had been in trouble on a number of occasions.
Turkey’s president said the intelligence service there was also looking into the attack.
Gokmen Tanis was not known for extreme religious beliefs, although he was once captured on video criticising a female reporter’s clothing.
A 47-year-old woman called Angelique told Algemeen Dagblad that Tanis was a drug user with a criminal record who was facing trial for raping her in 2017. She said he had recently been freed from custody after violating the conditions of an earlier release.
The case is due to return to court during the summer.
Several reports said his marriage had fallen apart and that he was also linked to other pending criminal cases involving bicycle theft and a burglary at a bike shop.
What happened on Monday?
At about 10:45 local time (09:45 GMT), police were called to reports of a shooting on board one of the city’s trams at the 24 Oktoberplein junction.
One witness told local media that “a man started shooting wildly”.
Another witness told Dutch public broadcaster NOS that he had helped an injured woman when the tram came to an emergency stop.
“I looked behind me and saw someone lying there behind the tram,” he said. “People got out of their cars… and they started to lift her up.
“I helped to pull her out and then I saw a gunman run towards us, with his gun raised,” he said. “I heard people yell ‘Shooter! Shooter!’ and I started to run.”
The gunman then fled the scene, leading to the manhunt which lasted for much of Monday.
A number of raids were reportedly carried out and counter-terrorism officers were pictured patrolling the streets near to where the attack happened. Police surrounded a building not far from the scene of the attack and arrested Mr Tanis on Monday evening.