The sheriff overseeing the hunt for missing 84-year-old Nancy Guthrie has issued an update.

It comes as investigators believe she may have been deliberately “targeted” – but warned the suspect could “absolutely” attack again.

Pima County Sheriff Chris Nanos made the chilling admission as pressure continues to mount over the month-long search for the grandmother, who disappeared on February 1. It comes after a mystery man who claimed he “saw Nancy 5 days ago” offered chilling new proof.

Despite suggesting police have an idea about the motive, Nanos said detectives cannot be completely certain and refused to reveal further details about what they think happened.

Speaking to NBC News on Thursday night, he said, “We believe we know why he did this, and we believe that it was targeted, but we, we can’t, we’re not 100% sure of that.”

Nanos said it would be wrong to assume the wider public is not at risk, stressing that people should remain vigilant.

“So it’d be silly to tell people, ‘Yeah, don’t worry about it. You’re, you’re not his target.’ Don’t think for a minute that because it happened to the Guthrie family, you’re safe. No, keep your wits about you,” he added.

The sheriff declined to discuss any further theories about Guthrie’s disappearance as the investigation continues.

The disappearance of Nancy Guthrie has now stretched into its sixth week.

Nancy was abducted from her home in the Tucson area. Police believe she was taken from the property during the early hours of February 1.

Surveillance footage recovered from a doorbell camera showed a masked and armed intruder outside the home during the night. Investigators say the individual appeared to tamper with the camera before it was disconnected.

Bloodstains found at the property were later confirmed to belong to Guthrie, raising serious concerns about what may have happened after she disappeared.

Detectives have not revealed the extent of her injuries but say the circumstances inside the house were “very concerning.”

Guthrie is the mother of NBC Today co-host Savannah Guthrie. The TV presenter stepped away from her broadcasting duties as the search has issued several emotional appeals for information.

During her recent return to the NBC show, Savannah thanked her colleagues for their support and prayers, particularly for “caring about my mom as much as I do.”

In five words, she revealed what sustains her during this difficult period, saying, “I’m holding onto my faith. I still believe. And as my mom would say, ‘Where else would I go?'”

Her family has since offered a $1 million reward for information that leads to Nancy’s recovery or the arrest of whoever took her.