Police said emergency response teams were at the scene to treat victims and investigate the shooting.
A Dutch police officer shot and killed two family members and himself at a home in the city of Dordrecht on Monday evening, a police source said.
A fourth relative was injured, said the source, who could not be identified because the investigation was ongoing.
"Three people were killed in the shooting incident in Dordrecht's Heimerstein (neighbourhood). One person was seriously injured," according to the official police statement on Twitter.
Emergency response teams were at the scene and a home in the neighbourhood had been cordoned off.
Dordrecht Mayor Wouter Kolff said on Twitter there had been "a very serious shooting incident" and that he was heading to the scene.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)