Blane, 56, and Susan Barksdale, 59, are wanted in the murder of Frank Bligh, who vanished when his home burned down on April 16, as well as other charges, including arson, police in Tucson said Tuesday.
Bligh's body was never found.
Susan Barksdale knew Bligh, who was 72, police said.
Bligh was a Vietnam veteran and in the Air Force Reserve, his brother, William, told ABC News.
"I knew Sue very good. … In fact, my wife and I, one of the times we visited my brother in Tucson, we had dinner with her, we went places with her, she was a very pleasant, nice person," William Bligh said. "Everybody got along good ... and somewhere along the line she met Blane."
The couple allegedly fled to upstate New York in May, where U.S. Marshals and a SWAT team surrounded their RV and took them into custody.
Police said that as they were finally being transported from Henrietta, New York, to Pima County, Arizona, they overpowered two security guards in Blanding, Utah, on Monday and allegedly stole their vehicle. That vehicle was later abandoned.
The couple is believed to have put the guards, one male and one female, in the back of the transport van. The Barksdales then allegedly drove the van to northeast Arizona, where they abandoned it, with the guards still "tied up in the van," according U.S. Marshal for the District of Arizona David Gonzales.
The guards needed several hours to get free from the van, which gave the Barksdales "a six or seven hour head start," Gonzales said.
Though the guards were not carrying any weapons when they were overpowered, there was a gun that was in a lock box in the transport van. That gun was never accessed by the Barksdales and was recovered by investigators, Gonzales said.
There was a third prisoner being transported to Tucson who remained in the van during the entire ordeal.
"He wanted to no part of it," Gonzales told ABC News. "He didn’t try to escape and he was kind of a victim himself."
The fugitives are believed to have gotten access to another vehicle through an acquaintance. Investigators believe they could be armed, but they are likely running low on funds and only have $30 that they stole from the guards.
"I would love to have these two people caught, and I would love to have the court system take over and do the justice that they deserve," William Bligh said.
"Blane has numerous tattoos on his arms and hands. The Barksdales' direction of travel is currently unknown. Investigators have information that they are possibly traveling through Arizona. They were last seen driving a red GMC Sierra pickup truck (license plate AZ: 127XTY) with damage to the front passenger side and rear bumper," Tucson police said in a Facebook post Tuesday.
Drivers were being urged to stay on the lookout for the duo, but authorities warned the public that the couple should not be approached.
"The FBI, US Marshals and Apache County Sheriff's Office are assisting in the investigation. If the Barksdales are spotted, please call 911 immediately. Anyone with possible information on their whereabouts is urged to call 911 or 88-CRIME," the police said.
The U.S. Marshals Service has announced they are offering a $10,000 reward for each fugitive.
Pima County said it was suspending use of the company that was transporting the prisoners, Security Transport Services, "pending a review of the incident/escape." The sheriff's department said it used the service as a cost-saving measure and had transported about 70 inmates so far in 2019.