Police in Tucson are racing against time to find 84-year-old Nancy Guthrie.

Now, a veteran Border Patrol agent is revealing a chilling reason why the person believed to be behind her disappearance may never be identified.

”We will not rest”

Nancy Guthrie, the 84-year-old mother of Today co-host Savannah Guthrie, has now been missing for five days, and authorities believe she may have been abducted. So far, no suspects have been identified.

On Wednesday, Savannah and her family made a tearful public plea, urging whoever took their mother to come forward.

”We will not rest,” Savannah Guthrie said in the video. ”Your children will not rest until we are together again.” She also adressed the reports of a ransom note, saying, ”Please reach out to us.”

But catching Nancy Guthrie’s kidnapper could prove extremely difficult. An expert warns that her abductor may never be found, and it all comes down to one troubling factor. Art Del Cueto, a longtime U.S. Customs and Border Protection officer who lives just minutes from Guthrie’s home, told the Daily Mail that the surrounding terrain presents a major obstacle for investigators.

The rugged Tucson landscape

Del Cueto is not involved in the case, but has years of experience tracking individuals through the rugged Tucson landscape.

The area around Guthrie’s home is remote and surrounded by dense desert vegetation, which Del Cueto says could easily conceal someone trying to flee.

“We’re on the southern border. You’re dealing with international crime all the time, and there are just too many variables to rule anything out,” he explained.

He added that Tucson’s proximity to Mexico could allow a suspect to disappear quickly, possibly before authorities even have a clear picture of what happened.

“If somebody gets spooked, they can make it into Mexico in under an hour and a half, that’s why authorities may not be sharing everything they know,” Del Cueto said.

Former FBI special agent weighs in

According to him, that combination of harsh terrain, limited visibility, and international access may be one reason investigators have been tight-lipped as the case unfolds.

Nancy Guthrie’s neighborhood has also been described by her neighbor, Morgan Brown, who lives just a quarter mile down the street from her home.

“If you step two feet off the road, you are basically in the thick of the cactus. It’s not gated at all. You just walk on the street and then there’s desert, so [they] thought she walked off into the desert or something, but she walks with a cane, so I can’t imagine why she would do that. It’s desert-y, scrubby mesquite trees and cactus and rocks everywhere,” Brown told US Magazine.

Del Cueto isn’t the only expert offering insight.

Former FBI special agent Dr. Bryanna Cox, now a criminology professor at the University of South Florida, has also weighed in on the case. She believes the abductor is likely a man in his 30s or 40s, based on the available details. She also believes that the person was stranger to Nancy.

”If it were a family member or somebody who knows the house, they wouldn’t have forced entry,” Dr Fox explained. ”If she knew them, they would have been likely to have carried out a ruse to get her to go with them and get into the vehicle.”

As the investigation continues, authorities have said time is critical — and the environment itself may be working against them. We’re praying that Nancy is found safe and unharmed!