U.S. Sen. Susan Collins said over the weekend that President Trump did not follow federal law when he fired inspector general Steve Linick on Friday without notifying Congress.

Collins made the statement on Twitter, and appeared to get a direct response from the president Sunday.

Linick, an inspector general with the U.S. State Department, was fired by the president at the request of Secretary of State Mike Pompeo, who accused Linick of undermining the work of the State Department.

The Office of Inspector General in each federal department is a government watchdog agency charged with ensuring government officials follow federal law. Collins, R-Maine, co-sponsored a 2008 law that protects watchdogs like Linick from being fired abruptly for political purposes.

“In 2008, I coauthored with former Sens. McCaskill and Lieberman The Inspector General Reform Act (P.L. 110-40), which among other provisions requires the President to notify Congress 30 days prior to the removal of an Inspector General along with the reasons for the removal,” Collins tweeted Saturday, hours after news of the firing. “The President has not provided the kind of justification for the removal of IG Linick required by this law.”

The President has not provided the kind of justification for the removal of IG Linick required by this law.

— Sen. Susan Collins (@SenatorCollins) May 17, 2020

On Sunday, Trump called out Collins in a tweet that appeared to be partly prompted by a CBS’ “60 Minutes” report featuring Dr. Rick Bright, a former federal health official who has criticized the Trump administration’s response to the coronavirus pandemic.

“This whole Whistleblower racket needs to be looked at very closely, it is causing great injustice & harm,” Trump tweeted. ” I hope you are listening @SenSusanCollins … ,” the president tweeted along with criticism of the show’s staff.

Linick was investigating possible abuse of power by Pompeo as well as U.S. arms deals with Saudi Arabia, according to the Associated Press and other media.

It was unclear whether the president is seeking something from Collins, who serves on several key Senate committees including the Intelligence Committee.

It also was not clear if Collins or her Republican colleagues will respond to the firing and lack of notice.

After a similar dismissal of a different inspector general last month, Collins and a fellow Republican senator wrote a letter seeking an after-the fact explanation, Collins said in a written statement provided to the Portland Press Herald on Monday. It’s not clear if they received one.

Collins said her comments on Twitter were in reference to the removal of the inspector general and not Bright’s allegations.

“As a long-time, strong supporter of our inspectors general, I am concerned about the president’s firing of IGs as well as the appointment of a political appointee from within the Department of Transportation to be the acting IG in that department.  I coauthored the 2008 law that requires the President to notify Congress and provide a justification for the removal of an IG.  It is not sufficient for the President to say simply that he has lost confidence in the official,” Collins said in her statement.

“The Inspectors General are key to accountability in federal programs and root out waste, fraud, and abuse and report to both the President and Congress.  I previously joined Senator Grassley in a letter to the President asking for an explanation for the removal of the Intelligence Community IG, Michael Atkinson.  I will continue to work with Senator Grassley to explore other remedies to ensure the independence of our government watchdogs, the Inspectors General.”

Congressional Democrats have demanded the administration turn over all records related to Linick’s firing, suggesting Pompeo may be responsible for “an illegal act of retaliation.”

Sen. Bob Menendez, D-New Jersey, ranking member of the Senate Foreign Relations Committee, called the firing a “Friday night massacre.” Menendez and his Democratic counterparts in the U.S. House have vowed to investigate.

U.S. House Speaker Nancy Pelosi, D-Calif., said Linick was “punished for honorably performing his duty to protect the Constitution and our national security.” She said Trump ”must cease his pattern of reprisal and retaliation against the public servants who are working to keep Americans safe, particularly during this time of global emergency.”

Note: This article was updated Tuesday, May 19, to make clear that Steve Linick served as inspector general in the U.S. State Department and that each federal department has a separate Office of Inspector General.