UTRECHT, Netherlands (AP) — Dutch police say they have arrested a third person on suspicion of involvement in the tram shooting in the city of Utrecht that left three people dead and five injured.

Public prosecution office spokesman Ties Kortmann said Tuesday that three people are now in custody — the alleged shooter, 37-year-old Gokmen Tanis and two others who were also arrested on suspicion of involvement in the shooting Monday morning.

Kortmann says Tanis is being held on suspicion of manslaughter with a possible terrorist motive, but adds that investigations are continuing into what drove him to allegedly open fire in a tram.

Authorities say they have not ruled out other possible motives and Dutch media citing his neighbors in Utrecht have speculated that the shooting may have been linked to a relationship.