In this frame grab from video provided by WLS-TV ABC 7 Chicago, authorities work a scene in Joliet, Illinois, Jan 22, 2024, after discovering multiple people shot and killed at three locations since Sunday in the Chicago suburbs. (CHICAGO SUN-TIMES VIA AP)

Authorities in Illinois searched on Monday for a man wanted as a suspect in the fatal shooting of eight people, including seven members of a family who were found inside two homes in the Chicago suburb of Joliet, police said.

There was no immediate word on a possible motive for the shootings, but the man sought in connection with the killings knew his victims, law enforcement officials said at a media briefing on Monday evening.

Police then entered Nance's residence, where five more bodies were discovered, bringing the total death toll at the three homicide scenes to eight

Local sheriff's deputies and agents for the FBI's fugitive task force were assisting in the manhunt, police said.

The suspect was identified by the Joliet Police Department as 23-year-old Romeo Nance, whom authorities said should be considered armed and dangerous.

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Authorities said the first known victim among the eight was a man found shot dead on Sunday afternoon in Joliet Township. He was identified only as a 28-year-old man originally from Nigeria who has been living in the US for about three years, police said.

An investigation of that shooting led deputies to an overnight stakeout in search of Nance, the registered owner of the suspected getaway vehicle, at his last known address in the nearby city of Joliet, about 35 miles (56 km)southwest of Chicago.

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Officers on Monday morning noticed blood outside a second home across the street from Nance's address, and inside found two people shot dead. Police then entered Nance's residence, where five more bodies were discovered, bringing the total death toll at the three homicide scenes to eight.

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"I've been a policeman 29 years. This is probably the worst crime scene I've ever been associated with," Joliet Police Chief William Evans said of the two adjacent homes.

A ninth person, a 42-year-old man, was left wounded but is expected to survive from yet another "random" shooting on Sunday that authorities said was linked to Nance's vehicle but who was not otherwise connected to the other victims.