An image captured by a security camera shows what the Federal Bureau of Investigation (FBI) describes as an armed individual appearing to have tampered with the camera at Nancy Guthrie's front door the morning of her disappearance at her home in Tucson, Arizona. Photo / Pima County Sheriff's Department, AFPAn image captured by a security camera shows what the Federal Bureau of Investigation (FBI) describes as an armed individual appearing to have tampered with the camera at Nancy Guthrie’s front door the morning of her disappearance at her home in Tucson, Arizona. Photo / Pima County Sheriff’s Department, AFP

‘Hour of desperation’