Video of masked prowler tops sheriff's list of clues to Nancy Guthrie's abduction

The Arizona sheriff leading the investigation into the abduction of U.S. television journalist Savannah Guthrie's elderly mother says the biggest clue by far in the nearly two weeks since she vanished is the video of a masked prowler tampering with her doorbell camera.

"That individual is who we're looking for," Pima County Sheriff Chris Nanos said in an interview with Reuters as the search for 84-year-old Nancy Guthrie, presumed kidnapped for ransom from her home near Tucson, stretched into its 13th day.

"Are there others? We don't know that until we find him, or other evidence comes in to indicate that, but right now, he's who we want. Somebody out there knows who this is," Nanos said.

Nanos was referring to the release earlier this week of then-newly discovered video footage showing an armed man -- wearing a ski mask, gloves and a backpack -- tampering with Nancy Guthrie's Google Nest doorbell camera outside her house shortly before she vanished.

"The strongest evidence is that video," Nanos said. "That's really what we're focused on. We've got to find that guy. And that's what everybody is trying to do."

Experts have said that investigators were likely seeking to bring facial recognition analysis to bear on the video to produce a composite image of a suspect that they can run against a national database that includes all U.S. drivers with Real ID licenses.

The sheriff said the release of the video, which took days to retrieve and reassemble from discarded digital data likely left unarchived on Google servers, immediately generated a flood of nearly 5,000 calls from tipsters. By then, he said, the sheriff's department and FBI had already fielded some 30,000 calls together.

He said investigators are "constantly taking in video" from other sources, ranging from traffic cameras to license-plate scanners to neighborhood surveillance cameras.

"Everything is being gathered in and looked at," he said. "It is a long process."

Nancy Guthrie was last seen on January 31 when family dropped her off at her home following an evening dinner with them, and relatives reported her missing the following day, authorities said.

The sheriff has said the elder Guthrie had extremely limited mobility and could not have wandered off far from home unassisted, leading investigators to conclude early on that she had been taken against her will.

Traces of blood found on her front porch were confirmed by DNA tests to have come from Guthrie, officials said last week. Law enforcement and family members have described her as being in frail health and in need of daily medication to survive.

At least two purported ransom notes have surfaced since she disappeared, both delivered initially to news media outlets and setting two deadlines that have since lapsed.

Savannah Guthrie, 54, co-anchor of the popular NBC News morning show "Today," has posted several video messages with her brother and sister, appealing to their mother's captors for her return, pleading for the public's help in solving the case, and even expressing a willingness to meet ransom demands.

Nanos confirmed to Reuters that no proof of life has surfaced since the abduction, but he was quick to add: "there's not been any proof of death either."

The sheriff went on to reaffirm his working presumption that Nancy Guthrie remains alive.

"Hope is sometimes all we have, it really is," he said. "I have a team of 400 officers from federal government, state government, local government. I have a community of a million people here who are invested in this, who want her back. Sometimes all we have to go on is hope. I'm not going to kill that."

The FBI on Thursday doubled the reward offered for information leading to the location of Nancy Guthrie, or the arrest and conviction of a suspect in her abduction, to $100,000.

-Herbert Villarraga, Jana Winter and Jasper Ward/Reuters