Washington (CNN) Lt. Col. Alexander Vindman , the National Security Council's top Ukraine expert who testified last week before House impeachment investigators , has no intention of leaving his post at the National Security Council, officials familiar with the matter said.

Vindman, an Army officer who is currently detailed to the National Security Council, is expected to stay on in his role until his time is finished next summer, people around him believe, despite the recent spotlight he's found himself in.

While Vindman intends to stay, it's not clear whether President Donald Trump or those close to him will seek his ouster. The President has characterized him as a "Never Trumper," and one senior administration official would not rule out a presidential decision removing him from the council.

A number of current and former administration officials have sat for depositions in the impeachment inquiry. But for now, Vindman is the only current White House official remaining in his post after sitting for the lengthy interview.

Investigation

House Democrats are investigating Trump's efforts to press for an investigation into former vice president Joe Biden and his son Hunter Biden, who sat on the board of a Ukrainian gas company. There is no evidence of wrongdoing by either Biden in Ukraine.

For more than 10 hours, Vindman testified that he reported concerns about Trump's July 25 call with the leader of Ukraine to the top National Security Council lawyer within hours, and said some of the changes he tried to make to the since-published transcript were left out, though he didn't say why. Later, he was told not to discuss the call with anyone else.

Despite testimony that will likely only fuel further inquiry, Vindman has been seen at work in the building next door to the White House where his office is every day since. His return, multiple sources say, has been a mixture of business as usual with a pervasive sense of tension among staffers who are hoping to stay above the political fray that has consumed the typically inconspicuous council.

One of those staffers is his twin brother, Yevgeny, who is also an Army lieutenant colonel and lawyer with the National Security Council. It's still unclear if Yevgeny will also be called to testify, though he's also not expected to leave right now.

Never Trump accusations

Since his appearance, Trump has attempted to sow doubt about Vindman's political ties, calling him a "Never Trumper witness" and implying more information would be revealed about him in the coming days. Since then, Trump has not offered more information and the White House hasn't clarified his intentions, though unsubstantiated claims have surfaced online that Vindman criticized America in conversations with Russian officers during a military exercise in Germany several years ago. There is no proof to the accusation.

Sources say Vindman, a Purple Heart recipient who was injured by a roadside bomb in Iraq, has no concerns about whatever information the President holds. A person close to Vindman dismissed the idea that he harbors any political motivation that factored into his decision to come forward. They also disputed claims he was critical of the US while overseas.

After Trump hung up the phone with Ukrainian President Volodymyr Zelensky in July, Vindman had immediate concerns that what he said would "undermine US national security," Vindman testified before lawmakers last week.

"I did not think it was proper to demand that a foreign government investigate a US citizen, and I was worried about the implications for the US government's support of Ukraine," Vindman said in his opening statement. "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."

Sense of duty

Despite those concerns, Vindman didn't consider resigning, a person close to him says. Instead, he saw it as his sense of duty to make his complaints about the president and his inner circle's conduct known. It wasn't a moral decision, but seen as passing it up the chain of command before returning to work.

"I did convey certain concerns internally to national security officials in accordance with my decades of experience and training, sense of duty, and obligation to operate within the chain of command," he testified, according to his opening statement.

By testifying before the House Intelligence, Foreign Affairs and Oversight and Reform Committees, Vindman defied a White House edict not to cooperate with the impeachment inquiry. But a person close to Vindman said he felt like he had no other option; because he is not a political appointee, Vindman is not afforded the same executive privilege rights as other staffers who have been called to testify. By not going, it was a stay of execution, this person said.

As Democrats prepare to move their investigation into the public eye, there is a chance Vindman could be called to testify again. Democratic lawmakers saw his explosive testimony -- including that he "did not think it was proper" for Trump to ask Zelensky to investigate a political rival -- as helpful to their case.

Though Trump will likely continue to attempt to discredit him, people close to the President say, Vindman may have documents to back up his assertions. One person close to Vindman described him as a diligent notetaker who was often seen carrying 3x5 notecards around the office.