May 7, 2008 -- A Florida grand jury will decide whether a 15-year-old girl whose disappearance triggered an Amber Alert should be tried as an adult in the murder of a man she and her boyfriend allegedly beat and suffocated.

Authorities in Florida issued arrest warrants on first-degree murder charges against the teenager, Amanda Morgan Leppert, and Toby Lee Lowry, 22. Authorities say the couple fled the state April 25 in a stolen pickup truck belonging to murder victim James Thomas Stewart, 66.

Both remain in custody in El Paso, Texas, where police found them Saturday, 1,600 miles from home, panhandling by an interstate highway after a motorist recognized Leppert from a nationally publicized Amber Alert.

Stewart was found dead inside his Melrose, Fla., home May 1. His Toyota Tacoma was missing from his driveway. An autopsy found that he had been beaten, stabbed and suffocated before he died, authorities said.

"Mr. Stewart had been viciously beaten with two metal rods and had been stabbed multiple times with a knife," Putnam County Sheriff Dean Kelly said at a press conference Tuesday. "The autopsy also revealed that Mr. Stewart had been suffocated with a plastic garbage bag that had been put over his head."

Leppert was originally reported missing April 22. Her mother told police that she feared her daughter may be with Lowry, a Florida man with a lengthy criminal history in Putnam and Clay counties.

Lowry was released from a 20-month prison sentence last summer. Kelly said Leppert and Lowry may have become romantically involved sometime last fall. It was unclear how they'd met, but Kelly said it could have been over MySpace.

After Stewart's family reported to police that the 66-year-old, who's hard of hearing, had not contacted them in days, police entered the house and discovered the murder scene.

Leppert had left behind her phone at Lowry's house when she disappeared, Kelly said at yesterday's press conference, and authorities saw that a call had been made from Stewart's home to Leppert's phone April 25. With the pickup truck missing and Stewart dead, authorities had reason to believe that Lowry -- and perhaps Leppert -- were involved in his death. A warrant was issued for Lowry's arrest on charges of auto theft and interfering with child custody.

Authorities tracked the pair in the truck through three states to Texas. According to a timeline provided by the Putnam County Sheriff's Office, the two stopped at a Gainesville, Fla., Wal-Mart after the murder and bought new clothing.

They dumped the cap to their victim's trunk and picked up a hitchhiker in Georgia who authorities said was unaware of the homicide. The trio decided to head for California. The vehicle is spotted in Biloxi, Miss., April 29; Crowley, La., April 30; and finally Katy, Texas, May 1.

Two days later, a motorist reported seeing the couple, along with the hitchhiker they'd picked up in Georgia, panhandling Saturday in El Paso.

Authorities believe that Leppert and Lowry spent the first few days following her disappearance in Putnam County on the lookout for a crime of opportunity. They spent time in a wooded area behind Stewart's house before Leppert knocked on the man's door and asked to use his phone.

"There was no prior relationship," Kelly said Tuesday of the alleged decision to attack Stewart. "They cased the area looking for an easy mark."

After placing the call to her own phone, she returned to Lowry and reported that Stewart was vulnerable. Later that night, Kelly said, the two entered the house and committed the murder.

Authorities said that the Amber Alert worked as planned in this case. If Leppert had been 18, they would not have been able to publicize that she was missing as widely.

At 15, Kelly said, they had to at least assume there was a possibility that she was being held against her will.

"We said all along that she was a victim until we proved otherwise," Kelly said. "And we've proved otherwise."

Florida authorities expect the pair to be extradited from Texas to Florida by the end of this week. A grand jury will likely hand down an indictment on the murder charges in the next few weeks.