The next batch of documents from Special Counsel Robert Mueller's Russia investigation is set to drop Friday, unveiling new details about two of President Trump's former associates.

The first, a document that should explain why investigators scrapped the cooperation agreement they had with Trump's former campaign manager Paul Manafort.

That filing could also shed new light on Manafort's business dealings or consulting work for pro-Kremlin interests in Ukraine.

The other document, a sentencing memo for Trump's former lawyer Michael Cohen, who's now working with investigators.

He pleaded guilty to financial crimes and to lying to Congress in a Mueller case.

The focus for that filing, whether Cohen revealed anything new to supplement his admission last week, that toward the end of President Trump's campaign, Cohen asked for help from the Kremlin for a Trump skyscraper in Moscow.

Mueller's investigation into possible collusion between Russia and Trump's 2016 campaign has infuriated the president.

Just Friday morning, he took aim at the Special Counsel and his investigation, calling it a "witch hunt," as he has on previous occasions.

Also mentioned in the tweet, former FBI director James Comey, who will testify before two house committees Friday behind closed doors.

Trump's firing of Comey in 2017 is also part of Mueller's investigation.