A drifter previously convicted of killing and beheading hikers in Florida and Georgia was sentenced Thursday to four additional life sentences in federal prison for kidnapping and murdering a North Carolina couple in a national forest.

Gary Michael Hilton, 66, pleaded guilty in March 2012 to killing John and Irene Bryant in 2007. Hilton camped out for victims before he ambushed the Hendersonville couple, who were in their 80s, as they hiked in the Pisgah National Forest in Transylvania County. He also pleaded guilty to robbery and firearms offenses.

U.S. District Judge Martin Reidinger ordered that Hilton's federal life sentences be served consecutively with an earlier life sentence for murdering 24-year-old hiker Meredith Emerson in northern Georgia in 2008. Federal sentences do not have the possibility of parole.

Hilton was already on Florida's death row for killing Cheryl Dunlap, 46, of Crawfordville, Fla., who was found dead in north Florida's Apalachicola National Forest where Hilton had camped. Emerson, of Buford, Ga., and Dunlap were beheaded.

The bodies of the four victims were found over a span of several months starting in late 2007.