John Dowd, the defense attorney who was leading President Donald Trump’s team in the special counsel Robert Mueller’s investigation, has resigned from representing him, The New York Times reported Thursday.

The revelation comes as Trump has increasingly vented his frustration toward the Russia investigation and Mueller. Dowd invited intense scrutiny last weekend when he publicly called for deputy attorney general Rod Rosenstein to shut down the Russia investigation, which Dowd characterized as corrupt and biased against Trump.