WASHINGTON — Top Democrats at the deposition of Lt. Col. Alexander Vindman, the top Ukraine expert on the National Security Council, said his testimony Tuesday was “extremely disturbing” and praised him for appearing despite attacks from the White House.

The closed-door deposition before House impeachment investigators lasted more than 10 hours.

Once it concluded, House Intelligence Committee Chairman Adam Schiff, D-Calif., told reporters that he hopes Vindman's example of patriotism "will be emulated by others."

Schiff said that he was "deeply appalled" by attacks made against Vindman on Fox News Tuesday night.

"The suggestion that because he's of Ukrainian origin, that he has some dual loyalty...this purple heart recipient deserved better than that scandalous attack," Schiff said.

Regarding reported attempts by GOP lawmakers to get Vindman to reveal the whistleblower's identity, Schiff said that Trump would love to "punish" the whistleblower. He also said the president's comments and actions have "jeopardized the whistleblower's safety."

"The President's allies would like nothing better than to help the president out this whistleblower. Our committee will not be a part of that. We will not stand for that," he said. "They have the right to remain anonymous. They certainly should not be subject to these kind of vicious attacks and other words and actions that threaten their safety for doing their patriotic duty," he said about whistleblowers.

Earlier in the day, Acting House Oversight Chairwoman Carolyn Maloney, D-N.Y, told NBC News she found Vindman’s remarks “extremely, extremely, extremely disturbing” as she left the deposition. Maloney refused to answer any other questions about Vindman’s testimony.

Vindman, appearing voluntarily under congressional subpoena, was set to tell members of Congress conducting an impeachment inquiry of President Donald Trump that he was on the phone call between Trump and Ukraine’s leader in which Trump asked for an investigation into the Bidens — and that he raised concerns about it.

Vindman considered Trump’s request that Ukraine investigate his political rivals so damaging to American national security that he reported it to a superior, according to his opening statement obtained by NBC News.

Rep. Debbie Wasserman Schultz, D-Fla., a member of the House Oversight Committee who was present for the deposition, told NBC News that Vindman was a “very credible” witness and said his testimony "corroborated the testimony of other witnesses" that "really drew a direct line to the President, and those around him and their interest in withholding foreign aid through Ukraine that was vital, as well as insisting on investigations into Biden."

Vindman’s testimony, she said, has "actually filled in more of the puzzle pieces."

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Wasserman Schutlz said the Republicans present for the deposition were trying to get Vindman to reveal the identity of the whistleblower.

"What the Republicans are trying to do very clearly in their questioning is try to front door or back door Lt. Col. Vindman into revealing who the whistleblower is, even though in his testimony he says he doesn't he didn't know," she said.

"They've been unsuccessful," she added.

Leaving the deposition, Rep. Eric Swalwell, D-Calif., said that he was concerned that Republicans in the room were trying to out the identity of the whistleblower, which caused a tense moment between Swalwell and Rep. Mark Meadows, R-N.C.

"My concern inside the room is that you know there, there’s an intent to out the whistleblower, and you know risk that person's life which is why we're trying to protect them," he said. "And that's what the quote, unquote tense moment was about."

According to his prepared remarks, Vindman, the National Security Council director for European affairs, will tell members of the committees investigating Trump that he was on the July 25 call between Trump and Ukrainian President Volodymyr Zelenskiy, making him the first witness to the call to appear before congressional investigators in the Democrats’ impeachment inquiry.

"I was concerned by the call," Vindman's opening statement says. "I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government’s support of Ukraine."

"I realized that if Ukraine pursued an investigation into the Bidens and Burisma, it would likely be interpreted as a partisan play which would undoubtedly result in Ukraine losing the bipartisan support it has thus far maintained," his statement adds. "This would all undermine U.S. national security. Following the call, I again reported my concerns to NSC’s lead counsel."

The call is at the center of the impeachment inquiry against Trump launched by House Democrats. Critics say that Trump’s alleged pressure on the Ukrainians amounted to an abuse of power designed to help him in the 2020 presidential election.

Vindman served multiple overseas tours as an infantry officer and received the Purple Heart after being wounded by an improvised explosive device while in Iraq. He joined the National Security Council in July of 2018.

Vindman will also tell Congress that he is not the unnamed whistleblower whose complaint sparked what would become the impeachment inquiry now underway, according to the statement, and that he does not know who the whistleblower is.

In addition, he will say that he twice reported his concerns to the National Security Council’s lead attorney, John Eisenberg, once after a July 10 meeting about comments made by U.S. ambassador to the European Union Gordon Sondland, and also after Trump's phone call with Zelenskiy. His statement says he never had any direct communications with Trump.

Attacks on witness

After details of Vindman’s opening statement emerged Monday night, Trump, as well as Republican allies of the president, attacked the former soldier.

“Supposedly, according to the Corrupt Media, the Ukraine call ‘concerned’ today’s Never Trumper witness," Trump tweeted. "Was he on the same call that I was? Can’t be possible! Please ask him to read the Transcript of the call. Witch Hunt!”

Supposedly, according to the Corrupt Media, the Ukraine call “concerned” today’s Never Trumper witness. Was he on the same call that I was? Can’t be possible! Please ask him to read the Transcript of the call. Witch Hunt! — Donald J. Trump (@realDonaldTrump) October 29, 2019

On Monday night, Fox News host Laura Ingraham and John Yoo, a former official in the George W. Bush Justice Department, discussed on Ingraham’s show whether Vindman, who was born in the former Soviet Union and fled with his family to the U.S. as a child, could have effectively conducted espionage because, according to The New York Times, Ukraine officials sought his advice in dealing with Trump personal attorney Rudy Giuliani's efforts regarding Ukraine.

Rep. Ami Bera, D-Calif., who as a member of the House Foreign Affairs Committee was present for Vindman’s deposition, defended Vindman in an interview on MSNBC Tuesday, saying he “is someone without impunity.”

“For any of my colleagues to try to smear his reputation — that’s just not fair,” he said.

Some Republicans also defended Vindman.

Rep. Liz. Cheney, R-Wyo., said at a press conference with GOP leadership Tuesday morning that the attacks on Vindman were “shameful.”