Updated: 4/22/19 5:20 p.m.

On Monday, the U.S. House of Representatives Judiciary Committee Chairman, Jerrold Nadler, sent out a subpoena to Don McGahn, the former White House counsel to testify before the panel in its investigation of potential obstruction of justice by President Donald Trump.

Democrat Jerry Nadler claims the committee asked him for documents from McGahn by May 7 and for him to testify on May 21. An attorney on behalf of McGahn was not available for comment.

A report by Robert Muller, publicly released on Thursday by the Justice Department said Trump asked McGahn to fire Mueller because he was investigating suspected Russian interference during the 2016 U.S. election and possible coordination between Trump campaign members and Moscow officials.

“Mr. McGahn is a critical witness to many of the alleged instances of obstruction of justice and other misconduct described in the Mueller report,” Nadler mentioned.

Mueller’s report claimed that the 22-month long investigation had not confirmed that the Trump campaign conspired with the Russians. However, Mueller did find “multiple acts by the president that were capable of exerting undue influence over law enforcement investigations.”

Nadler claimed Mueller’s report “outlines substantial evidence that President Trump engaged in obstruction and other abuses.”

He said, “it now falls to Congress to determine for itself the full scope of the misconduct and to decide what steps to take in the exercise of our duties of oversight, legislation, and constitutional accountability.”

According to the report on Mueller, Trump directed McGahn back in June 2017 to tell Rod Rosenstein, the Justice Department’s No. 2 official, that Mueller had conflicts of interest and should get removed. McGahn did not carry out the order.