Authorities are hunting for a man who shot and killed eight people across three locations in the suburbs of Chicago, Illinois.
The suspect remains at large.
Police in Will County and the city of Joliet said they did not know of a motive for the killings.
Joliet Police Chief William Evans did say the victims were known to the suspect, named as 23-year-old Romeo Nance.
“I’ve been a policeman 29 years, and this is probably the worst crime scene I’ve ever been associated with,” Mr Evans said during a news conference outside the Joliet homes on Monday evening.
One victim was found on Sunday, with the remaining seven discovered on Monday at three separate locations, authorities said.
Police also believe another shooting in Joliet that wounded a man on Sunday is connected to the attacks.
Mr Evans added that the victims found on Monday in the houses were family members.
The FBI’s Fugitive Task Force is assisting local police in the search for the suspect.
Emergency services have also warned the community on social media that the man should be considered “armed and dangerous”.
Joliet Police said in a Facebook post on Monday afternoon that they were investigating “multiple” people found dead.
It also shared the man’s photo and images of a vehicle, identifying the car as a red Toyota Camry.
The Will County Sheriff’s Office also shared images of the same car on Facebook on Monday and said it had been seen at the scenes of two separate shootings on Sunday afternoon.
Will County Chief Deputy Dan Jungles said during the news conference that police deputies had been staking out one of the houses since Sunday evening in case the suspect in the first fatal shooting they discovered returned to them.
Mr Jungles said he did not have any indication yet of how long the people in the houses had been dead and that autopsies are pending.