JACKSONVILLE, Fla. -

A registered sex offender from Jacksonville dropped 15-year-old Alyssa Frank off at a Defuniak Springs Wal-Mart on Tuesday afternoon and took off, according to the Polk County sheriff who issued an Amber Alert for the girl several hours earlier.

Law enforcement personnel across the state continue to search for William Joe Mitchell, a career criminal who was living on Jacksonville's Westside from Jacksonville after his most recent release from prison last December.

"He's a predator and a pedophile. We know that he lured this 15-year-old away after some period of possibly weeks of communication," Polk County Sheriff Grady Judd said.

Judd said Mitchell had taken the teenager into Alabama before returning to Florida. The girl told officials that Mitchell dropped her off at Wal-Mart and told her he was going somewhere for about five minutes and that if she drew any attention to herself he was going to kill her. Officials believe his real intent was to drop her off.

"He looked for an area to dump her, and for that we're grateful," Judd said. "We're relieved because she's alive and she's well. However, other children are not safe as long as our suspect is at large."

Authorities were told he has a gun.

The Amber Alert was cancelled at 1:30 p.m., less than 12 hours after authorities realized Frank had left her Central Florida home with William, whom authorities said she met on MySpace.com.

Authorities said she snuck out of her house in Bartow just before 3 a.m. on Monday. She told friends she was running away for love.

Early Tuesday morning when Polk County investigators learned she apparently ran away with Mitchell -- a 46-year-old registered sex offender whose last known address was in the 1400 block of Lane Avenue in Jacksonville.

Mitchell, who goes by the name BillyMitch, is a white man, 5 feet 10 inches tall, 158 pounds, with brown hair and blue eyes. He has several tattoos: the name Lisa, a cross and the word Love on his fingers. On his right arm he has a tattoo that reads "We" and the name Bill.

He may be traveling in a 2000 model black Chevrolet Lumina, Florida tag number G025EL.

Early Tuesday, Judd called Jacksonville Sheriff John Rutherford and St. Johns County Sheriff David Shore and asked for their help.

"I've asked for them to assist as if this violent sexual offender had the child in their county," Judd said at an early-morning news conference. "I think that's a possibility because that's the area he knows best."

Jacksonville police and agents of the Florida Department of Law Enforcement were at Mitchell's Lane Avenue apartment when Channel 4 arrived at 5:30 a.m. Tuesday.

Mitchell was released from prison last December after serving just over four years for a conviction for lewd and lascivious battery on a child in St. Johns County. He has 15 previous convictions dating back to 1985 on charges of armed robbery, aggravated battery, making a bomb threat, auto theft and a weapons charge. Most of his previous offenses were in St. Johns County.

Anyone with any information on the whereabouts of Mitchell is asked to contact the Polk County Sheriff's Office at 863-533-0344, 800-226-TIPS or 911.