Congressional investigators have released email showing a former IRS official wondered if Senator Chuck Grassley should be audited to see how he responded to an invitation that mistakenly was sent to her.

Lois Lerner is at the center of the controversy over IRS scrutiny of tax documents from conservative groups. Lerner got an email in 2012 from a group that actually was inviting Grassley to an event and offering to pay for Grassley’s wife to attend. Lerner asked a co-worker via email if Grassley should be audited to find out if he accepted. That IRS colleague advised against it and the matter apparently was dropped.

The House panel investigating the IRS calls it “shocking” and “unbelievable” that an IRS official would even think of launching an investigation of “a sitting Republican United States Senator.” Grassley says the incident is “very troubling” and the kind of thing that “fuels the deep concerns many people have about political targeting…by officials at the highest levels” in government.

Grassley says neither he nor his wife attended the event Lerner learned about from the mislabeled email invitation. The congressional committee which released the email exchange blacked out the name of the event’s sponsor.