The photos and video released by the FBI and Pima County Sheriff's Department show a man wearing a ski mask, gloves, backpack and what appears to be a gun holster.
The images recovered from a Google Nest camera on the front doorbell of Nancy Guthrie's Tucson, Arizona, home were recorded at 3am on February 1, a day after her family last saw her.
At one point in the video, the person appears to try to block the camera with foliage gathered nearby, then appears to damage it.
The individual's head is down when approaching the door, which suggests awareness of the camera's location, the law enforcement official said.
Police have said the camera was disabled in the early hours of February 1.
Guthrie's pacemaker disconnected from her phone in the pre-dawn hours of February 1, when she presumably was kidnapped.
Guthrie disappeared hours after relatives dropped her off at her home on January 31.
Relatives reported her missing the following day when she failed to show up for Sunday church services. Law enforcement officials have said they had no suspects or persons of interest in the case.
"Law enforcement has uncovered these previously inaccessible new images showing an armed individual appearing to have tampered with the camera at Nancy Guthrie's front door the morning of her disappearance," FBI Director Kash Patel wrote in an X post accompanying the images.
Patel was at the investigation's Tucson command post on Monday, the law enforcement official said.
At least two ransom notes were delivered initially to news media.
The elder Guthrie's disappearance has attracted wide attention.
White House press secretary Karoline Leavitt began her press briefing on Tuesday by saying she and President Donald Trump had just reviewed the newly released images.
"The president encourages any American across the country with any knowledge of the suspect to please call the FBI, who continue to assist state and local authorities who are leading this investigation on the ground," Leavitt said.
Savannah Guthrie and her siblings have made several videos pleading for the public to help with tips and for the kidnappers to return their mother or communicate with them directly.
The family has said that they would pay a ransom.
Savannah Guthrie shared the new images on Instagram on Tuesday with the caption: "We believe she is still alive. Bring her home."
