US federal agents have captured one of two inmates who escaped from a prison in Arizona, but are still searching for the second convict and a suspected accomplice.
Tracy Province was arrested in the US state of Wyoming, 60 miles (96km) away from Yellowstone National Park.
The manhunt intensified after the fugitives were linked to the murder of a couple in Oklahoma.
Authorities are now chasing leads in Wyoming.
"They consider themselves as Bonnie and Clyde," said US Marshal Services spokesman David Gonzales. "This is very, very serious business."
'On the run'
John McCluskey, who escaped from prison with Province 10 days ago, and suspected accomplice Casslyn Welch are believed still to be on the run.
"Rest assured, we are going to be on McCluskey like a cheap suit," said Mr Gonzales.
News of Province's arrest came soon after more than 100 agents and armed park rangers were deployed to search Yellowstone National Park.
The authorities tracked Province to Meeteetse, Wyoming, after receiving a phone call from a woman, who had spoken to the inmate on the steps of the town church.
Province was carrying a handgun and a hitchhiking sign when he was arrested.
Officials say Province, McCluskey and inmate Daniel Renwick escaped from Arizona State Prison after Ms Welch, McCluskey's fiancee and cousin, threw wire cutters over the fence of the jail.
Renwick was arrested in Colorado on 1 August.
Prior to Province's arrest, the authorities suspected the three were headed to Canada.