Sen. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.) told MSNBC Thursday that the integrity of the U.S. justice system "took a real blow" with Attorney General William Barr Bill BarrHarris faces pivotal moment with Supreme Court battle Hillicon Valley: DOJ proposes tech liability shield reform to Congress | Treasury sanctions individuals, groups tied to Russian malign influence activities | House Republican introduces bill to set standards for self-driving cars McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE's classification of the Mueller report.

"Our justice system and the integrity of that justice system took a real blow today with the presentation of General Barr and also his four-page summary weeks ago," she said while appearing on "All In with Chris Hayes."

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Harris added that in the wake of the report, Congress's job is now "oversight."

"I am looking forward to General Barr coming before the Judiciary Committee," said Harris, who sits on the committee. She noted that she believes he is scheduled to appear May 1 and also called for special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE to appear before Congress.

Barr released a redacted version of the Mueller report Thursday. He preceded the release with a press conference in which he defended President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE and explained why he did not determine that the president obstructed justice.

Some Democrats and media figures questioned whether it was appropriate for Barr to hold the press conference before releasing the report.

A few weeks before the release, Barr issued a summary of the report in which he said that the report provided no evidence of collusion between Russia and the Trump campaign and not enough evidence to pursue an obstruction of justice charge against Trump.

Harris previously served as a prosecutor and as California's attorney general. She is among more than a dozen people competing for the 2020 Democratic presidential nomination.