Rep. Jim Jordan (R-OH) didn't hide his surprise during a House Judiciary Committee hearing on Thursday in which FBI Director Robert Mueller told the lawmaker he wasn't aware of the details surrounding the FBI's probe of the IRS.

In a heated exchange, Jordan blasted Mueller for not being able to give names of investigators heading the investigation.

"This is the most important case in the country for the past six weeks and you don't know who the most important person is, leading the case?" Jordan asked.

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"Not off the top of my head," Mueller replied.

But Jordan didn't stop there, and instead continued to press Mueller in a series of questions on the topic.

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"Is it appropriate for the one doing the audit to give the information to the people he's investigating and not give that information to the oversight committee? Is that how an investigation is supposed to work?" Jordan fired. "I can't comment on what is appropriate," Mueller replied.

"You've had a month to investigate, and you can't even tell me who the lead investigator is? This is what happened. You can't even tell me what happened?"

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'He's the Jack Kevorkian of the Republican Party!'