Rep. Paul Ryan (R., Wis.) lit into IRS Commissioner John Koskinen over the missing Lois Lerner emails at a Friday House Ways and Means Committee hearing, flatly telling him he didn't believe his excuse for them being gone.

The emails of Lerner, the former tax-exemption chief at the center of the investigation into IRS targeting of conservative groups, were reported lost in a "hard drive crash," an explanation which Koskinen said was on the line.

"I'm sitting here, listening to this testimony, I don't believe it," Ryan said. "That's your problem. Nobody believes you. The Internal Revenue Service comes to us a couple years ago and misleads us and tells us no targeting is occurring. Then it said it was a few rogue agents in Cincinnati. Then it said it was also on progressives. All of those things have been proven untrue."

Ryan called Koskinen's explanation for the loss of the emails "unbelievable."

"You are the Internal Revenue Service," he said. "You can reach into the lives of hard-working taxpayers and with a phone call, an e-mail or a letter you can turn their lives upside down. You ask taxpayers to hang onto seven years of their personal tax information in case they are ever audited and you can't keep six months worth of employee e-mails? And now that we are seeing this investigation, you don't have the e-mails, hard drives crashed. You learned about this months ago. You just told us, and we had to ask you on Monday."

This is not being forthcoming, he said.

"This is being misleading again," Ryan said. "This is a pattern of abuse, a pattern of behavior that is not giving us any confidence that this agency is being impartial. I don't believe you. This is incredible."

Koskinen retorted he'd had a "long career" and never been told no one believed him.

"I don't believe you," Ryan said again.

Rep. Sander Levin (D., Mich.) snapped at Ryan to let Koskinen answer a question, and Ryan yelled back, "I didn't ask him a question!"

"I control the time," Ryan said. "I have not yielded time. I control the time."

Chairman Rep. Dave Camp (R., Mich.) had to invoke regular order to stop Ryan from being interrupted.

"Here's what being forthcoming is," Ryan said. "If we are investigating criminal wrongdoing, targeting of people based on their political beliefs and the emails in question are lost because of a hard drive crash that is apparently unrecoverable, which a lot of IT professionals would question, and you don't tell us about it until we ask you about it, that is not being forthcoming."