A National Security Counsel (NSC) staffer discussed President Donald Trump's July 25th call with Ukrainian President Volodymyr Zelensky with people outside of the counsel, Fox News reported. During the conversation, the staffer described the call as "outrageous."

President Trump's former special assistant who worked on European and Russian affairs, Fiona Hill, is set to provide a deposition to Congress next week, although it's unknown whether or not she helped prep for the call or received any readout of the call.

Hill worked for ex-National Security Advisers H.R. McMaster and John Bolton, until she left her post in July.

Former U.S. envoy to Kiev Marie Yovanovitch is also set to testify in front of Congress next week. Trump and those close to him have described Yovanovitch as a "rogue employee with an anti-Trump bias. She was ousted in May amid alleged attempts by Trump attorney Rudy Giuliani to press Ukraine into investigating Democratic presidential candidate Joe Biden and his son," Fox reported.

U.S. Ambassador to the European Union Gordon Sondland also plans to provide a deposition before a joint committee, despite the State Department directing him not to appear. He decided to testify after House Democrats subpoenaed him on Wednesday.

The whistleblower behind the Ukraine saga doesn't want to testify in front of Congress. Instead, he wants to submit written testimony. The House and Senate Intelligence Committees have not made a decision on that yet.

President Trump has said he has a right to know who the whistleblower is, especially because the person was wrong about what took place on the call. Democrats, however, have said the whistleblower's identity needs to remain anonymous because of safety concerns and the possibility of media scrutiny.