Dutch prosecutors say they are investigating a possible terrorist motive behind the shooting which killed three people and wounded five on a tram in the city of Utrecht.
Security forces arrested a Turkish-born man, 37-year-old Gokmen Tanis, after a seven-hour manhunt following Monday's incident.
Prosecutors said he is suspected of three fatal shootings, possibly with terrorist intent. Two other suspects were also in custody, police said, but their role was unclear.
"Up to this point, a terrorist motive is seriously being considered," prosecutors said in a statement, citing "the nature of the shooting and a letter found in the getaway car".
It remains unclear whether Tanis, who has a history of run-ins with law enforcement, was acting on political beliefs or a personal vendetta.
"Other motives are not being ruled out," the statement said.
The three Dutch victims were identified as a 19-year-old woman and two men aged 28 and 49. Three others, ranging from 20 to 74 years old, were critically injured in the shooting.
Prosecutors said they had so far not been able to establish a connection between the victims and the suspected gunman.
Utrecht went into lockdown in the aftermath of Monday's shooting on a tram just after the morning rush hour.
Flags flew at half mast on government buildings across the Netherlands on Tuesday in tribute to the victims.
