United Kingdom, March 13 -- Police believe Nancy Guthrie's abductor "could strike again" but won't share a possible motive.

The 84-year-old mother of Today show star Savannah Guthrie has been missing since January, and Pima County Sheriff Chris Nanos has opened up about the ongoing investigation.

Asked if the abductor "could strike again", Nanos told NBC Nightly News: "Absolutely.

"We believe we know why he did this, and we believe that it was targeted, but we're not 100 percent sure of that, so it'd be silly to tell people, 'Yeah, don't worry about it. You're not his target.'

"Don't think for a moment because it happened to the Guthrie family you're safe. Keep your wits about you."

While he wouldn't publicly elaborate on a motive, h...