Dutch police launched a large-scale probe Sunday after finding the bodies of three people including a policeman at a home in the small eastern village of Kekerdom near the German border.
"A police team of some 20 investigators on Sunday afternoon started their investigation," after the bodies were discovered earlier during the day, Dutch police said in an online statement.
The bodies of two men and a woman were found around noon (1000 GMT) by a neighbour who earlier noticed one of the victims' pets was very agitated, the local De Gelderlander newspaper said on its website.
"The relationship between the police officer and the other two victims is being investigated," the police statement added, saying "all scenarios are being looked at at the moment".
Gelderland-Zuid police spokesman Paul Koetsier confirmed a shooting incident to AFP but declined to give further details. The names and ages of the victims were not released.
Kekerdom is some 14 kilometres (nine miles) east of Nijmegen, situated next to the Duffeltdike, a popular cycling route in the area.