The suspect is currently on the run, police said.

One of the people killed was found Sunday in a home in Will County, seven others were found Monday at two homes in Joliet, police informed.

Police in the city of Joliet and Will County said they did not know of a motive for the killings, but said the man knew the victims, an Associated Press report mentioned. The FBI's fugitive task force was assisting local police in the search for the suspect, Joliet Police Chief William Evans said.

The victims were found Sunday and Monday at three separate locations, authorities told reporters Monday evening, several hours after warning on social media that the man should be considered “armed and dangerous.”

Authorities suspect that another shooting in Joliet that left a man injured on Sunday is connected to the string of violence. Authorities, however, would not discuss their evidence, they said.

“I've been a policeman 29 years and this is probably the worst crime scene I've ever been associated with,” Evans said during a news conference outside the Joliet homes Monday evening.

Will County Chief Deputy Dan Jungles said during the news conference that officers had been monitoring one of the houses since Sunday evening over possibilities that the suspect in that day’s shootings may return to them. When no one showed up, officers finally went to the door of one of the houses and no one answered. Officers then tried the other house, which they knew was linked to the first house and found the first bodies.

Jungles didn’t divulge any further details, however, added that he didn’t have any indications yet of how long the people in the houses had been dead.

Joliet Police Chief William Evans said the victims found Monday in the houses were family members, adding that while the suspect knew them, it is not ascertained whether it was members of the suspect's family. 

Joliet Police had said in a Facebook post earlier on Monday afternoon that they were investigating “multiple” people found dead and shared the man’s photo and images of a vehicle.

Authorities identified the vehicle as a red Toyota Camry.

On Monday, the Will County Sheriff’s Office shared images of the same car on Facebook and said it had been seen at the scenes of two separate shootings Sunday afternoon.

(with AP inputs)