WASHINGTON (AP) — Senate Democratic leader Chuck Schumer is calling on the nation's 74 inspectors general to protect government whistleblowers amid President Donald Trump’s ouster of key government officials in the impeachment probe.

In a letter Monday to the Defense Department inspector general, Schumer said Army Lt. Col. Alex Vindman has been “viciously attacked" by the Republican president after “bravely stepping forward to tell the truth.”

Vindman, a White House national security council official when he testified before the House impeachment inquiry, was removed Friday and reassigned.

Vindman’s twin brother, Lt. Col. Yevgeny Vindman, also was asked to leave his job as a White House lawyer.

Also out Friday was Gordon Sondland, who had been Trump's ambassador to the European Union. Sondland was among 17 people who provided public and private testimony in the impeachment proceedings.

The firings, alongside efforts to name the still anonymous government whistleblower whose complaint about Trump's call with Ukraine sparked the impeachment probe, demand attention, Schumer said.

Similar letters are being sent to all 74 IGs calling on them to take immediate steps to investigate any “instances of retaliation against anyone who has made, or in the future makes, protected disclosures of presidential misconduct to Congress or Inspectors General."

Federal employees have rights, including under the whistleblower law, that ensure they are protected through the inspector general offices and are able to provide information to Congress, as part of the legislative branch's oversight role.

The White House has stood by the dismissals.