Four people were killed on Monday evening in the Dutch city of Dordrecht in what police described as a "family drama".
An initial police statement indicated that a 35-year-old man as well as two children, girls aged eight and 12, had died and that a fourth person, a woman, had been hospitalised in a "worrying condition".
But police later said the 28-year-old woman, the mother of the two girls, had also died.
Authorities said "there are strong indications" that the shooting in the city's Sterrenburg district is "a family drama" and that the father, a police officer in Rotterdam, maybe the shooter.
An investigation to determine the "nature and circumstances" of the shooting has been launched.
Dordrecht Mayor Wouter Kolff said on social media that he sympathises with all those involved in the "very serious incident".
He later announced that a public gathering would be held on Tuesday evening to commemorate the family and that the municipality had opened a community register.
"This family drama understandably brings up a lot of emotions in Dordrecht especially for relatives, the neighbourhood, friends, classmates, teammates and the police organisation. Let us support each other," Kolff said.