Police, who did not give the precise number of victims, said all those who died were adults but that the cause of the incident last evening in Wurenlingen was unknown.
A news conference would take place later today. Neighbours alerted police after hearing gunshots after 11 pm (2100 GMT) and officers subsequently discovered several dead bodies inside and outside a building. Emergency services workers, however, had been unable to give a cause of death, police said in a statement. The identification of the victims was underway.