A LETTER THAT CHANGES EVERYTHING: On day 42, investigators reveal a message from the suspected kidnapper warning, “Those who come next should beware of me.”

“Don’t think for a minute that because it happened to the Guthrie family, you’re safe,” said Pima County Sheriff Chris Nanos in a March 12 interview

The lead investigator in the disappearance of Nancy Guthrie is raising concerns that her apparent abductor will strike again.

During a new NBC News interview, Pima County Sheriff Chris Nanos shared insight into the investigation as the search for Nancy — who is Today co-host Savannah Guthrie’s mother — continues for a sixth week.

Nanos said that authorities believe Nancy was “targeted,” while also warning that no one should rule out the possibility that the suspect could “absolutely” strike again.

“Criminal minds are criminal minds,” the Arizona sheriff told NBC’s Liz Kreutz in a clip from the interview, which aired on the Today show on Friday, March 13.

“We believe we know why he did this and we believe that it was targeted, but we’re not 100% sure of that,” Nanos continued. “So it’d be silly to tell people, ‘Don’t worry about it. You’re not his target.’ You could be.”

He did not explain why the authorities believe that the suspect could strike again and didn’t expand on other theories surrounding Nancy’s Feb. 1 disappearance.

However, Nanos added that they remain hopeful that the “mixed” DNA found at Nancy’s house will lead investigators to “somebody.”

Sheriff Nanos previously spoke about the possibility of Nancy being targeted in an interview which aired on the Today show on Feb. 18.

“I think this was an individual who had a target for whatever reason, and he has made it tough, but I’ve got some pretty tough investigators too,” said Nanos.

The Pima County Sheriff’s Department and the FBI haven’t publicly named a suspect or confirmed whether Nancy is alive or dead. At least three people, who are not suspected of any wrongdoing, have been detained and released amid their search for potential leads.

More than a week after Nancy was reported missing, authorities released footage of a masked person tampering with her doorbell camera. The FBI estimated the individual to be “a male, approximately 5’9” – 5’10” tall, with an average build,” but the suspect has not been identified.

Nancy’s relatives have been ruled out as potential suspects.

The FBI is offering a $100,000 reward for anyone with information that could lead to Nancy’s return, while the Guthrie family is offering a $1 million reward of their own.

Anyone with information about Nancy Guthrie’s disappearance is asked to please contact 1-800-CALL-FBI (1-800-225-5324) or the Pima County Sheriff’s Department at 520-351-4900.