(CNN) -- The suspect in the shooting deaths of two motorists in Mississippi will be charged with capital murder Friday, a police spokesman said.

Police arrested James D. Willie, 28, of Sardis, Mississippi, after tests concluded that a gun he had was used to kill two people along roadways in the northwestern part of the state, according to a statement from the sheriff's office in Tunica County, near the Arkansas and Tennessee state lines.

The killings stirred panic and fear for drivers across the state.

Willie is "no stranger to law enforcement" and will make an initial appearance before a judge in the next day or so, Mississippi Highway Patrol spokesman Warren Strain said.

Formal capital murder charges are forthcoming, he said.

"Hundreds of man hours have been devoted to tracking down and arresting this individual," Mississippi Gov. Phil Bryant said.

Willie is a convicted felon with a long criminal record, Strain said.

Investigators had raised the possibility that someone posing as a police officer was to blame for the shooting deaths of 74-year-old Tom Schlender and 48-year-old Lori Anne Carswell, which happened 55 miles apart.

On Friday, though, Strain said it does not appear that the shooter impersonated a police officer.

The motive and many details of the shootings remain unclear, he said.

Investigators arrested Willie on Tuesday on an unrelated offense, after a woman said he raped her.

The woman said she was abducted and taken to an apartment, where there was an altercation, Strain said. There may have been shots fired there, and police rushed to the scene, he said.

Police seized a semiautomatic Ruger handgun Willie had.

"It was determined after testing by state Crime Lab scientists, the weapon matched the weapon used in two murders in northwest Mississippi last week," the sheriff's office statement said.

One day earlier, authorities said they were questioning a different suspect in the case.

Authorities said a different man was picked up after stopping two drivers Wednesday night. That man, identified as James Lucas, 45, of Yazoo City, was driving a blue Mercury Marquis that used to be a police car and still had flashing blue lights behind its grille, Humphreys County Sheriff Investigator Sam Dobbins said.

Dobbins said investigators searched Lucas' home and found handcuffs and fake badges.

Early Friday, it was unclear what, if any, connection Lucas had to the case.

CNN's Ed Lavandera contributed to this report.

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