Four people found dead on Boxing Day (26 December) in an upstate New York basement apartment have now been identified, and are thought to be victims of what police are describing as a quadruple homicide.
Police said that two women living together as partners, aged 36 and 22, and the older woman's two children, an 11-year-old boy and a 5-year-old girl, were killed in a "savage" attack.
The New York Post reported that after the discovery of the crime shocked police in upstate New York.
Troy police chief James Tedesco said: "After being in this business for nearly 42 years, I can say I have not seen savagery like this. Only a person of savagery would do something like this."
Their bodies were discovered by the manager of the property after concern about the family had been raised by neighbours.
Police believe that there is "no imminent danger to the community" of Rensselaer County, but officials have warned people to be on guard.
City Councilman Mark McGrath said: "I have strong confidence in the Troy detectives and state police that they're zeroing in on someone as we speak.
"The brutal, horrific nature of the crime suggests that this is someone who is psychopathic at the very least."
Police remain in the area while further investigations are carried out at the apartment and the surroundings.