The bodies of an elderly man, an elderly woman - who were not related - and a younger man with defensive wounds had been dead for several days in the Tenafly home, Bergen County Prosecutor John L. Molinelli said.
The slayings were "definitely not a murder-suicide," and it was not clear who may have killed them, he said.
Authorities said the house had not been ransacked and there were no signs of burglary.
The victims' names were not released pending notification of family members.
Molinelli said the elderly man's daughter asked her husband to check on the residents because she had not heard from them for some time. The man went to the home, walked in through the unlocked back door, saw one body and called Tenafly police. Police found all three victims upstairs.
They set up two tents and a generator in front of the three-story home, which has an attached garage. Sheriff's officers and the county medical examiner were at the scene, along with local police and detectives from the prosecutor's office.
