Investigators in the Netherlands say they have found a memo hinting at a possible terrorist motive behind Monday's deadly shooting in Utrecht.

Dutch police have arrested 37-year-old Gokmen Tanis from Turkey for allegedly opening fire in a tram, killing three people.

Police and prosecutors said on Tuesday they have found a letter in the suspect's getaway car that hints at a terrorist motive. They did not say what was written in the memo.

Turkish media initially said Tanis fired at a relative he had fallen out with. But Dutch investigators said they have not been able to find a link between the suspect and the victims -- a woman and two men.

Investigators add that personal problems and other motives have not been ruled out.

They are also investigating two men, aged 23 and 27, who were taken into custody for their suspected involvement in the shooting attack.

NHK