Federal agents Monday captured one of the two convicted killers who escaped from an Arizona prison, and were still searching for the other inmate and a suspected accomplice.
The trio were feared headed for Canada, and the RCMP had issued a warning on them Sunday.
Tracy Province was arrested with a handgun in northwest Wyoming, about 100 kilometres outside of Yellowstone National Park, said David Gonzales, the U.S. Marshal for Arizona.
The other inmate, John McCluskey, as well as suspected accomplice Casslyn Welch, were still on the lam.
"They consider themselves as Bonnie and Clyde," Mr. Gonzales said. "This is very, very serious business."
Efforts to find the trio intensified after they were linked to a double homicide in New Mexico.
Mr. Province, Mr. McCluskey and Daniel Renwick escaped from a private, medium-security Arizona state prison near Kingman on July 30 after authorities say the 44-year-old Ms. Welch threw wire cutters over the perimeter fence. Welch is McCluskey's fiancee and cousin.
The three later kidnapped two semi-truck drivers at gunpoint and used the big rig to get away, authorities said. The group left the drivers unharmed in the truck at a stop just off Interstate 40 in Flagstaff and then fled. Renwick was arrested Aug. 1 in Colorado.
The manhunt intensified Saturday after forensic evidence linked the two inmates and Ms. Welsh to the killings of an Oklahoma couple. New Mexico State Police spokesman Peter Olson declined to elaborate.
The badly burned skeletal remains of Linda and Gary Haas - both 61 and from Tecumseh, Okla. - were found in a charred camper Wednesday morning on a remote ranch in eastern New Mexico. Their pickup truck was found later 160 kilometres west in Albuquerque.
Mr. Province was serving a life sentence for murder and robbery out of Pima County, Ariz. Mr. McCluskey was serving a 15-year prison term for attempted second-degree murder, aggravated assault and discharge of a firearm out of Maricopa County, Ariz.
Mr. Renwick had been serving a 22-year sentence for second-degree murder.
Publicizing their photographs in newspapers and on television, including a segment Saturday night on "America's Most Wanted," has helped generate tips, investigators said. A series of billboards featuring the three are also planned.