Fox News contributor John Solomon, formerly a columnist and executive vice president for The Hill, has emerged in the impeachment hearings as a key figure who pushed conspiracy theories that President Donald Trump used to pressure Ukraine to investigate a political opponent. The Hill’s Editor-in-Chief Bob Cusack announced on Monday morning that the outlet will be reviewing and correcting Solomon’s columns as necessary.

In his columns, Solomon repeatedly laundered disinformation from Trump’s personal lawyer Rudy Giuliani to push the false narrative that Ukraine interfered in the 2016 presidential election on Democrats’ behalf, smeared former U.S. Ambassador to Ukraine Marie Yovanovitch, and falsely claim that former Vice President Joe Biden withheld aid to Ukraine to shut down an investigation into a company his son Hunter was associated with . Multiple witnesses have testified in the impeachment inquiry that Solomon’s columns contained information that was made up and were based on “non-truths.”

On Monday, CNN media reporter Oliver Darcy posted on Twitter an email from Cusack which announced the Hill will be “reviewing, updating, annotating with any denials of witnesses, and when appropriate, correcting any opinion pieces” of Solomon’s that have been referenced in the impeachment inquiry.

ProPublica also reported recently that Solomon was involved in an apparent pay-to-play operation at The Hill, which involved him courting a conservative group for a six-figure advertising deal and also quoting its director in the Hill’s news content.

Solomon took to Fox News just yesterday, threatening to sue his critics.