(CNN)Five people died in the northern Swiss town of Wuerenlingen after residents heard shots fired late Saturday, federal police said.
Responding officers from Aargau County Police found their bodies lying outdoors and inside a residence.
A large group of officers and investigators worked through the night on the investigation, which is ongoing, Aargau police said in a statement. The state prosecutor's office has opened a criminal inquiry.
Authorities have not established a motive or identified the victims.