STERLING, Ill.—The FBI launched a manhunt Tuesday for an ex-con suspected of killing eight people in two states, including a 93-year-old man, a child and a couple whose blood-soaked dogs were found roaming a motel parking lot.

Federal and local officials announced a $25,000 reward for the arrest of Nicholas T. Sheley, 28, and said he should be considered armed and dangerous. He was last seen in St. Louis, authorities said.

Police in Galesburg, in northwestern Illinois, said they had a warrant for Sheley’s arrest on charges including first-degree murder, aggravated battery and vehicular hijacking in the death of Ronald Randall, whose body was found Monday behind a Galesburg grocery store. An autopsy shows the 65-year-old died of blunt force trauma to the head.

Officials said the other victims all appeared to have died in the same manner.

Public records show Sheley has multiple convictions for robbery, drugs and weapons charges and has spent three years in prison.

The killings began with the beating death of 93-year-old Russell Reed, a Sterling man whose body was found stuffed in the trunk of a car Thursday. Sheley also is from Sterling, a town of 15,000 about 100 miles west of Chicago.

On Monday, police discovered the bodies of two men, a woman and a child in an apartment in Rock Falls, a town near Sterling. Police said someone asked them to check on the victims, and that they believe one of them was connected to Reed.

State Police Sgt. Thomas Burek said Sheley was an acquaintance of one of the people found inside the apartment.

The Galesburg grocery store where Randall’s body was discovered Monday is about 60 miles southwest of Rock Falls.

Also Monday, the bodies of a man and woman were found behind a gas station in the St. Louis suburb of Festus, Mo., about 250 miles south of Galesburg. Investigators were looking for the couple’s pickup truck.

Bill Baker, with the St. Louis Area Major Case Squad, identified the couple as Tom and Jill Estes of Sherwood, Ark., who had checked into a Comfort Inn in Festus on Friday and were last seen late Sunday. The couple’s dogs were found in the hotel parking lot, unharmed but covered with blood.

Festus is within 50 miles of both St. Louis and Collinsville, Ill., both cities where police say Sheley was seen Monday.

On Tuesday morning, police in tactical gear searched a Collinsville apartment building for a person of interest in the Festus killings, but “were unable to locate the guy,” Collinsville police Sgt. Rich Wittenauer said.

Sheley’s uncle, Joe Sheley, 47, of Sterling, told The Associated Press that Nicholas Sheley had recently struggled with drugs and that his rap sheet include arrests for home invasion.

“He’s been in trouble many times over the years, but something like this, yeah, it’s out of character,” Joe Sheley said. “He’s got a temper like anybody else. Just doesn’t want to be messed with. Won’t back down. But to go looking for a fight, looking for trouble, no.”

Sheley spent nearly three years in the Illinois Department of Corrections.