The person who killed 7-year-old Somer Thompson may have preyed on children before, making the search for the second-grader's slayer that much more urgent, police said.
Clay County authorities said they are running frustratingly low on credible leads despite receiving more than 1,000 tips about Somer's kidnapping and murder. But "America's Most Wanted" host John Walsh said county Sheriff Rick Beseler is "looking very hard at certain people.
"The sheriff and I both feel that it's a predator who has probably done it before," Walsh, who has been following Somer's case since she disappeared last week, told "Good Morning America" today.
He pointed to a string of four child disappearances in the Jacksonville area about 20 years ago that have never been solved.
"I would hate to think this is a serial child killer who has raised it's ugly head," Walsh said, noting that it's not unusual for such a predator to come out of "retirement."
Somer disappeared Oct. 19 while walking home from school with her twin brother and older sister, 10. She ran ahead after a squabble with her siblings and vanished shortly after.
Somer's body was found Wednesday in a Georgia landfill after detectives followed garbage trucks from Somer's Orange Park, Fla., hometown in search of clues.
A public visitation will be held tonight; her funeral is Tuesday.
Police say they've checked out nearly all the more than 90 sex offenders living within a three-mile radius of Somer's home and repeated searches of a vacant house near where the little girl disappeared have not yet yielded any obvious clues.
Police are hoping that samples taken from the house and the landfill where Somer's body was found will give investigators something to go on.
"All I want is to happen is that my baby didn't die in vain and we catch him," Somer's mother, Diena Thompson, said.
Walsh called Somer's killer a "cool, calculating predator" who may strike again.
"People should be on high alert there because there is a child killer at large," he said.
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