Serial Killer

The IRS sent Billy Wallace a letter, warning him that he was due for an audit.
Billy shrugged, tore up the letter, and flushed it down the toilet.
The next day, the auditor was standing in front of his cell, looking in his briefcase.
“You say your profession is: Serial Killer, correct?” said the auditor.
“That’s correct,” said Billy.
“And how many people have you killed?”
“One.”
“Just one?” asked the auditor. “Don’t you need more than one to be classified as a serial killer?”
“I was just getting started.”
The auditor fined him for lying on his tax return.