Senate Minority Leader Chuck Schumer on Monday sent letters to all 74 federal inspectors general demanding that they immediately investigate the "shameful" and "illegal" White House retaliation against whistleblowers who have raised alarm about President Donald Trump's misconduct and abuses of power.

Schumer's demand comes after Trump on Friday fired National Security Council staffer Lieutenant Colonel Alexander Vindman and U.S. Ambassador to the European Union Gordon Sondland, both of whom testified against the president as part of the House of Representatives' impeachment inquiry.

"Without the courage of whistleblowers and the role of inspectors general, the American people may never have known how the president abused his power in the Ukraine scandal."

—Senate Minority Leader Chuck Schumer

The New York Times described the terminations as the beginning of Trump's "purge" of his staff as he seeks revenge for the impeachment proceedings, which ended just last week with Senate Republicans' nearly unified vote to acquit. An anonymous Trump adviser told CNN that the Vindman and Sondland firings were "flushing out the pipes."

"Although LTC Vindman lived up to his oath to protect and defend our Constitution by bravely stepping forward to tell the truth, he has been viciously attacked by the president and forced to endure threats to his and his family's safety," Schumer wrote in a letter to Glenn Fine, acting inspector general for the Department of Defense.

"These attacks are part of a dangerous, growing pattern of retaliation against those who report wrongdoing only to find themselves targeted by the president and subject to his wrath and vindictiveness," Schumer added. "They also include attempts to publicly identify the anonymous whistleblower who used the proper legal channels to initially report the president's attempts to compromise our national security for his personal benefit."

Schumer urged Fine to "take immediate action to investigate any and all instances of retaliation against anyone who has made, or in the future makes, protected disclosures of presidential misconduct to Congress or inspectors general."

The Senate Minority Leader also demanded that inspectors general notify Congress of the last time agency and department staffers were reminded of their legal rights to "make protected disclosures anonymously and free from reprisals."

"Without the courage of whistleblowers and the role of inspectors general, the American people may never have known how the president abused his power in the Ukraine scandal," Schumer wrote. "It is incumbent on you that whistleblowers like LTC Vindman—and others who put their lives on the line to protect our freedoms—are protected for doing what we hope and expect those who serve our country will do when called: tell the truth."

Read Schumer's full letter to Fine: