(CNN) One of the people accused of killing a 72-year-old man and overpowering two security officers to escape custody has been added to the US Marshals Service's list of the 15 most wanted fugitives.

Blane Barksdale, 56, along with his wife, Susan Barksdale, 59, may be getting help from white supremacists, US Marshal for the district of Arizona David Gonzales said Monday.

The couple escaped custody in late August as they were being extradited to face charges of arson, burglary and murder in connection with the death of Frank Bligh, a Vietnam veteran killed in April in Tucson, Arizona. The two had used a medical emergency to get the guards to pull over to the side of the road, and then overpowered them and threw them in the back of the van, Gonzales said last month.

"Somebody like Blane in prison -- with both local -- with both state and federal prison, would be associated with Aryan Brotherhoods, white supremacist gangs. So those are the type of individuals we think that might be assisting," Gonzales said at a news conference Monday.

"I don't think there's a question that there are people that are assisting in harboring these individuals, and it is a felony," he said.

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