One of the most absurdly ironic true crime moments ever involves Dennis Rader, the serial killer known as BTK.

After m*rdering at least 10 people between the 1970s and 1990s, BTK resurfaced in the early 2000s because he was angry that the public had stopped paying attention to him. He started sending taunting letters to police and local media again, basically demanding recognition.

At one point, he wanted to send the police a floppy disk containing messages. But before doing it, he actually asked them a question through one of his letters:

“Can I communicate with a floppy and not be traced to a computer? Be honest.”

The police publicly replied that it would be safe and that they couldn’t trace it.

So BTK trusted them.

He mailed the floppy disk.

The FBI checked the metadata and quickly discovered it had been used by someone connected to “Christ Lutheran Church.” The disk also contained traces pointing to a user named “Dennis.” Investigators linked it to Dennis Rader, president of the church council, and arrested him in 2005.

The funniest part is that after he was caught, Rader was reportedly genuinely offended that the police had lied to him. He apparently thought they would answer honestly because he specifically asked them to “be honest.” A serial killer basically got upset that the FBI didn’t play fair with him.