A top U.S. diplomat gave a private deposition Tuesday in the impeachment probe after House Democrats subpoenaed him following State Department efforts to block him from testifying.

His opening remarks prompted “sighs and gasps” from Democrat and Republican lawmakers who witnessed his deposition, Politico and CBS News report, citing anonymous sources.

House Democrats pursuing the impeachment probe have conducted all depositions behind closed doors. The Democrats have so far refused to release the transcripts of the witnesses’ testimony. Reporters and the public are forced to rely on second-hand accounts of what is taking place inside the deposition room.

CBS News reported:

Taylor’s opening statement was “lengthy,” and his testimony was “very dramatic” and “detailed,” according to members of the House committees conducting the impeachment inquiry. Another source said that Taylor’s testimony was “damning.”

A source who was in the room confirmed to CBS News that there were sighs and gasps — from both Democrats and Republicans — in reaction to Taylor’s opening statement.

Politico added:

President Donald Trump’s top envoy to Ukraine told House impeachment investigators on Tuesday of intense efforts by administration officials to secure investigations of Trump’s political rivals in exchange for a White House meeting with Ukraine’s president and critical military aid, according to sources in the room for the testimony.

William Taylor prompted sighs and gasps when he read a lengthy 15-page opening statement, two of the sources said. Another person in the room said Taylor’s statement described “how pervasive the efforts were” among Trump’s allies to convince Ukrainian officials to launch an investigation targeting former Vice President Joe Biden and another probe centering on a debunked conspiracy theory regarding the 2016 election.

During their deposition, U.S. European Union Ambassador Gordon Sondland and former Special Envoy to Ukraine Kurt Volker denied that the Trump administration pushed Ukraine to investigate Joe Biden and his son, Hunter.

Volker said he pushed Ukraine to investigate corruption allegations against Burisma Holdings, a Ukrainian company where Hunter served on the board of directors.

George Kent, a deputy assistant secretary of state, told impeachment investigators he warned the Obama administration that Burisma was corrupt when Hunter was working there.

Obama administration officials, however, “rebuffed,” his assertion, the Washington Post found.

The House Democrats’ impeachment inquiry stems from an intelligence community “whistleblower” complaint that accused Trump of “using the power of his office to solicit interference from a foreign country [Ukraine] in the 2020 U.S. election.” Trump and Ukraine have denied the allegation.

In a letter to House Democrats, the White House said it would not cooperate with the impeachment probe, dismissing the proceedings as unfair and “illegitimate.” House Speaker Nancy Pelosi (D-CA) has refused to hold a vote to authorize the inquiry.

U.S. Secretary of State Mike Pompeo has said his department will fulfill its legal obligations related to the impeachment probe. Nevertheless, Pompeo has described the process as “unfair” and a “silly gotcha game.”

The State Department has reportedly urged its employees not to testify before House impeachment investigators, a move that has triggered subpoenas issued by Democrats.

An unnamed official working on the impeachment investigation told NBC News on Tuesday:

In light of an attempt by the State Department to direct Ambassador William Taylor not to appear for his scheduled deposition, and efforts by the State Department to also limit any testimony that does occur, the House Intelligence Committee issued a subpoena to compel his testimony this morning.

As is required of him, Ambassador Taylor is now complying with the subpoena and answering questions from both Democratic and Republican Members and staff.

In a series of text messages that Volker provided to impeachment investigators, Taylor lamented that it is “crazy to withhold security assistance” from Ukraine.

Taylor’s concerns, however, stem from a Politico report that the Trump administration was withholding aid from Ukraine, not White House policy.

Rep. Andy Levin (D-MI), who witnessed Taylor’s deposition, described the State official’s testimony as “very troubling.”

“All I have to say is that in my ten short months in Congress — it’s not even noon, right? — and this is my most disturbing day in Congress so far,” Levin told CBS News.

Politico noted:

Rep. Jim Jordan (R-Ohio), the president’s lead defender in the room, was tight-lipped as he emerged from the closed-door deposition for a lunch break. He praised what he described as GOP lawyers’ effective questioning of Taylor but declined to say whether it yielded exculpatory information.

House Democrat-led Committees on Oversight and Reform, Intelligence, and Foreign Affairs are conducting the impeachment investigation. Jordan is the top Republican on the oversight and reform panel.