Adam Curtis Williams, 33, of Logan, Utah, was arrested by authorities in the Mexican state of Jalisco on Wednesday on felony theft charges, Kleberg County Sheriff Richard Kirkpatrick said.
Police say they want to talk to Williams because he may have been the last person to have had contact with James and Michelle Butler.
Police released a surveillance photo containing an image of Williams and another woman, identified as Amanda Noverr as they crossed the border into Mexico in a truck that belonged to the Butlers.
Debbie Van Loon, the sister of James Butler, told WMUR-TV in New Hampshire: "We're glad to hear the arrest has been made and await what's next."
The Butlers' bodies were discovered last week on a beach in a shallow grave off Padre Island, near Corpus Christi, Texas. James Butler, 48, was a Navy veteran and self-described full-time RVer. His wife Michelle Butler was 46. The couple had been traveling around the country and had stopped in Texas while on their way to Florida.
The couple's death are being investigated as homicides, authorities said, however, they have not released the cause of death.
Photo: Kleberg County Sheriff's Office