8-year-old girl found dead in Jacksonville, Florida

(CNN) -- The body of an 8-year-old girl who was reported missing late Friday from a Walmart in Jacksonville, Florida, was discovered Saturday morning, police said.

"This is a transition from an abduction investigation to a murder investigation," Jacksonville Sheriff's Office spokesman Shannon Hartley told reporters. "Obviously, we have the unfortunate answer that we didn't want to have."

After a woman called police late Friday to report that her daughter, Charish Lilly Perriwinkle, was missing from the store, authorities initially called on the public to help find the 4-foot, 3-inch, 60-pound girl, who had been wearing an orange sundress, purple flip-flops and a pink ribbon.

After the investigation revealed that the girl had been abducted, an Amber Alert was activated, Hartley said. He identified Donald James Smith, "a man with a very extensive criminal history" that included a kidnapping conviction, as a suspect.

On Saturday morning, police stopped Smith, 56, as he drove a white van southbound on I-95 in Jacksonville and detained him without incident, Hartley said.

"Obviously, having Mr. Smith in custody is a huge break for us," he said as the search for the girl was continuing. "We are very confident that he was the one that took her from the Walmart."

Hartley said he did not know how the girl had become separated from her mother. "I don't know if he lured her, I don't know if he snatched her," he said.

Soon after, Hartley said in a subsequent news conference, police followed a lead that took them four miles from the Walmart to a church, near which the body was discovered.

According to records from the Duval County Clerk of Courts, Smith's most recent convictions occurred last year on charges from 2009 for unlawful impersonation of a public employee and aggravated child abuse by willful torture, for which he was sentenced to a year in county jail.

"The first thing I would tell you is, as a parent, hug your children closely right now and know where they're at," Hartley said. "Just pay attention to them, keep them close."