Nancy Guthrie Died 'Shortly' After Kidnapping, Never-Before-Seen Note Claims

Nancy Guthrie died "shortly" after she was taken from her home in Tucson, Arizona ... according to a never-before-seen ransom note that cops say was sent days after she was snatched out of her bed in the middle of the night.

The Pima County Sheriff's Department released two notes received by local Tucson news outlet KOLD ... the first is a Feb. 2 ransom demand and the second, received on Feb. 6, claims Nancy "perished."

The note is addressed to the Guthries and it says ... "We did not fully grasp the seriousness of her physical condition. We never intended to hurt her, that was not our intention. She perished shortly after she was taken. We believe it was heart related."

The author says Nancy "is buried in nature" ... and they tell the family, "Nothing you could have done could have changed the outcome."

The note ends with an apology ... "We want your family to know this and hope you all can find peace. We are truly sorry."

In the ransom demand from February 2 -- which TMZ also received -- the alleged kidnappers lay out the demand for payment ... $4 million in bitcoin by 5 PM on Feb. 5 or $6 million in bitcoin by 5 PM on Feb. 9.

It's not clear when Nancy supposedly died, but again, the note claiming she was dead was sent Feb. 6.

Of course, Savannah Guthrie and the rest of the Guthrie family seemingly accepted she was dead months ago ... asking the kidnappers via social media only to tell them where her body is buried so they might bring her remains home and properly honor her.

Despite months of investigation -- Nancy was last seen 6 months ago today -- Pima County is still not closer to finding a suspect ... and they're asking the public to read these ransom notes in case they recognize the writer's "unique linguistic style."