Special counsel Robert Mueller, who is leading the investigation into Russia’s alleged meddling in the 2016 election, has a copy of a draft letter written by President Trump and a top White House aide detailing why he would terminate former FBI Director James Comey, according to a report.

Trump and Stephen Miller, a White House senior policy adviser, wrote the letter from Trump’s golf club in Bedminster, N.J., in May, the New York Times reported. It’s unknown what the draft letter said, but sources told the Washington Post it did not focus explicitly on the Russia probe.