CHICAGO (CBS) — The 2 Investigators tackle many topics, but this one’s a doozy, and begins with a riddle.

Who can declare someone dead? A doctor, perhaps a nurse. Well here’s a new one: the post office. CBS 2’s Dorothy Tucker introduces us to a woman “killed off” by a single piece of mail.

“I’m not dead,” Karen Naponelli said.

She can joke about it now, but Naponelli was in no mood to laugh when she got a letter from her bank, which read “please accept our condolences for your loss.”

“They’re writing this to whoever is my successor,” she said. “It does blow your mind. It’s unbelievable.”

US Bank assumed Naponelli was dead, because her October statement was returned as undeliverable, with a sticker attached to it, reading “deceased, unable to forward.”

Someone at the U.S. Postal Service returned the statement to the bank. But why? Diane Martin, the office manager at the Mount Greenwood post office told a reporter to leave when confronted about the incident.

Since Naponelli was dead on paper, she had to convince the bank she was alive before they started closing her account.

“Which meant my bills aren’t going to be paid,” she said.

To prove she had a pulse, Naponelli took her driver’s license, Social Security card, credit card, and anything else proving her identity straight to the bank. When one of the managers still had questions, she suggested, “if you Google me, you’ll find that I’m the only one in the world.”

That seemed to do the trick, but Naponelli still wanted to know how she ended up being declared dead.

“Someone made a mistake at that post office that could have really affected my life,” she said.

A post office spokesperson called it an “isolated incident” and speculated when the letter was returned, the “wrong sticker for the reason for nondelivery was applied.”

The post office apologized, and so did Naponelli’s bank. The bank told CBS 2 it will examine its policy for sending out letters to next of kin.