One of the reporters on the New York Times’ Pulitzer-winning exposé of President Donald Trump’s finances is leaving the publication following a falling out with the paper’s investigative team.

David Barstow, one of three authors of last year’s blockbuster investigation, is leaving the paper at the end of the month to lead the University of California Berkeley Graduate School of Journalism’s investigative reporting program.

“We are sorry to see him go but we hope that we get to work together on future projects,” Executive Editor Dean Baquet said in a memo to staff. “And we think he will be a great teacher for a new generation of investigative journalists.”

Barstow, 56, won a record four Pulitzer Prizes during his career as an investigative reporter at the Times, most recently with the Trump taxes story that exposed how the president and his siblings avoided paying taxes for years with efforts that the paper described as “outright fraud.”

The story wasn’t all good news though.

As The Daily Beast reported last month, the investigative team imploded in the months after publishing the major story after Barstow attempted to team up with one of the paper’s top-secret sources to ghostwrite a book. Barstow previously told The Daily Beast he was even considering leaving the Times to pursue the project, as ghostwriting is strictly forbidden under the paper’s ethical rules.

But the plan went sideways.

Editors caught wind of Barstow’s interest and told him not to pursue it. Barstow said he decided not to ghostwrite a book, but did try to help the source write a book proposal. The reporter sent multiple messages to the source and went so far as to make an unannounced visit to the person’s residence that left them “freaked out.”

Barstow did not respond to a request for comment Tuesday.

Baquet previously told The Daily Beast that Barstow did not violate the paper’s ethical guidelines, emphasizing that Barstow ultimately did not ghostwrite the book. Barstow denied any wrongdoing, saying it was not against the rules to consider it.

Nevertheless, Barstow’s pursuit of the source alienated his co-authors on the original Times story, Susanne Craig and Russ Buettner, who refused to work with him, sources said. Barstow said they pursued different tips. His byline did not appear on several subsequent Times investigative stories about Trump’s finances and taxes.