Article continues below advertisementThe search for Savannah Guthrie's missing mother, Nancy, may have taken a major turn.Troy Hillman, a retired Phoenix police sergeant who lives about two hours from Tucson, where the 84-year-old victim resides, said newly released footage from Nancy's Nest doorbell camera could be a critical development in the investigation.Article continues below advertisement"Overall, it's a huge break in the case," the former officer told a news outlet.Article continues below advertisementSource: MEGANew doorbell footage may help solve Nancy Guthrie's disappearance.