When I lived in Florida in the '90s, there was a big story in the news about a woman who was contacted by scammers claiming to be the FBI. They told her they needed her help to catch some criminal, and that they needed her to take out $5000 in cash from her savings account and give it to them in a public place. She did this, and they contacted her again and said they almost had the guy but they needed her to take out another $5000, which she did. She only got suspicious and called the cops after they tried this a third time but nobody showed up to receive the money. Apparently they assumed she was on to them and that the third time was a trap set up by the police.