DENVER -- Criminals are ready and waiting to make an innocent family's loss their gain.

"She was my sister. She was very sick and she died, and six months later I get this," said Shirley Geist holding a VISA bill. Geist never expected to get a bill from a credit card her sister had not used in years.

"I get a bill for $852.23 of which about $53 is finance charges and late charges because I did not get the December bill," Geist said.

Her sister, Florence Kavanaugh, passed away last June.

Geist had helped her pay off her debts, including the VISA account, nearly two years before her sister passed away.

"I had shredded the card," said Geist. "My mistake was I did not cancel it. I thought that once I paid the last bill and nobody got their hands on it, that would be the end of it."

Fraud prevention expert Mason Finks said Geist's mistake is one many people make.

"People often think, 'I've cut up the cards. The account is no longer being used. It's closed.' No. You contact the credit card company and you must officially notify them," said Finks.

Finks also said criminals have often preyed on the identities of the deceased, but now, they are moving even faster.

"Usually they try to move quickly before all the proper agencies are notified, before that credit card's been closed, before the credit agency's been notified, " he said.

Finks said something as simple as a name posted in the obituaries is all a criminal needs to get someone's personal information.

Geist realizes her mistake, but still wonders why the credit card company did not notify her of the unusual activity on the card.

"I'd like them to say, 'We're going to be a little more careful of who makes charges in the future," she said.

When contacted by 7NEWS, Citigroup said it is looking into the issue.

Finks points out there are several things people can do to protect themselves and their loved ones after a death has occurred. Move quickly to close all existing accounts and notify the Social Security office of the death.

It is very important, Finks said, to notify the credit bureaus.

He suggests calling back a few weeks later to confirm all the accounts are, in fact, closed.