An arrest warrant has been issued for the man seen in a photo released by the the Kleberg Co. Sheriff's Office on Monday.
Adam Curtis Williams is wanted on felony auto theft charges.
Kirkpatrick said his office believes 33-year-old Williams is the man seen driving James and Michelle Butler's 2018 silver four-door Chevrolet pickup truck on Oct. 21, towing their trailer, and is considered armed and dangerous.
Amanda Noverr, the woman believed to be in the truck, remains a person of interest in this case.
The pair is from Utah, and not local, as the Kleberg Co. district attorney suggested during Monday's press conference. The Kleberg Co. Sheriff's Office said it believes they Williams and Noverr are in Mexico, and are working with Mexican authorities to locate them.
Kleberg Co. Sheriff Richard Kirkpatrick said the pair was identified through a combination of the public's help since Monday's press conference and its investigative efforts.
The sheriff's office continues to seek any information about Williams and Noverr, and asks anyone who can help to call the Kleberg Co. Sheriff's Office at (361) 595-8500.
Williams previously has been arrested by U.S. Marshals in 2018 in Davis County, Utah.
James and Michelle Butler were residents of New Hampshire passing through Texas on the way to a seasonal job in Ft. Lauderdale, Fla. They were last seen alive at Padre Balli Park RV park on Oct. 15, according to the Kleberg Co. Sheriff's Office.
"They just were the perfect yin and yang with each other," said Stephanie van Loon, James Butler's niece. "They weren't separate people when they were together. They were just one unit."
They were reported missing on October 23, after friends and family lost contact with them.
Their remains were found in the dunes on Padre Island Oct. 27 in rural eastern Kleberg County when a reserve deputy trying to locate GPS coordinates in the course of investigating the Butlers' disappearance.