US President Donald Trump on Tuesday suggested that the Pentagon should review the conduct of a former White House national security aide who played a central role in the Democrats’ impeachment case and potentially consider disciplinary action against him.

Army Lt. Col. Alex Vindman, who until last week was detailed by the Pentagon to the White House, testified before the House impeachment panel that Trump inappropriately pushed Ukraine President Volodymyr Zelenskiy to investigate former Vice President Joe Biden and his son Hunter.

Vindman was ousted from his job on the White House National Security Council on Friday, just two days after the Senate acquitted Trump on abuse of power and obstruction of justice charges.

Trump has already been sharply criticized for pushing out Alexander Vindman and others who crossed him in the impeachment hearings.

Last week, the Senate voted to acquit President Trump on two articles of impeachment, marking the inevitable and historic end to a bitterly fought, divisive impeachment trial that will reverberate into the 2020 election and shape Trump’s presidential legacy.

The acquittal verdict was the final act of a four-month impeachment process that inflamed the partisan tensions simmering throughout the course of the Trump administration, the friction that boiled over during the State of the Union even though Trump left impeachment out of his speech.

After the Senate acquitted Trump of both charges, Senate Majority Leader Mitch McConnell would not say at a press conference whether he thought what Trump did was wrong, or if he agreed with some Republican colleagues it was inappropriate for a president to ask a foreign power to probe a political rival.

Earlier this month, the White House’s Office of Management and Budget (OMB) “has redacted portions of 24 documents pursuant to the Presidential Communications Privilege,” OMB’s deputy general counsel Heather Walsh said in a court filing, cited by US media.

Ukraine’s former president had said that he discussed investments with President Donald Trump’s attorney, Rudy Giuliani, in 2017, but that he never discussed Ukrainian companies with any US official.

On December 18, President Trump was formally impeached in a historic vote in the House of Representatives.