Attorney General William Barr on Sunday released a letter to Capitol Hill lawmakers summarizing the “principal conclusions” of Special Counsel Robert Mueller’s investigation into Russian meddling in the 2016 presidential race and possible collusion with Trump associates. The release of the long-awaited report comes about a month after he was confirmed to lead the Department of Justice once again.

Several Democrats -- Arizona Sen. Kyrsten Sinema, Alabama Sen. Doug Jones and West Virginia Sen. Joe Manchin -- joined nearly all the Republicans in confirming Barr.

Barr, 68, served as attorney general under the late President George H.W. Bush in the early 1990s. A Republican, he is a lawyer with Kirkland & Ellis in Washington, D.C.

Former Attorney General Jeff Sessions resigned from the post in 2018, and Matthew Whitaker was named acting attorney general.

Read on for five things to know about the respected attorney.

He already held this post in the first Bush administration

Barr has already held the position of attorney general, serving under the late President George H.W. Bush from 1991 to 1993.

Before that, he also served as deputy attorney general and assistant attorney general overseeing the Office of Legal Counsel.

At the Justice Department, Barr’s work ranged from combatting violent crime to investigating the Pan Am 103 bombing. He also coordinated counter-terror activities during the first Gulf War and spearheaded the response to the S&L crisis, according to his biography.

Prior to joining the Justice Department, Barr worked with the White House Domestic Policy staff for a year under then-President Ronald Reagan.

He has criticized the Mueller probe

In a 2017 interview with The Washington Post, Barr had a critique for Special Counsel Robert Mueller, who is spearheading the Russia investigation.

“In my view, prosecutors who make political contributions are identifying fairly strongly with a political party. I would have liked to see him have more balance on the group,” Barr said.

Trump has heavily derided Mueller’s team for being comprised of many registered Democrats and Democratic donors.

Barr has also said it was “understandable” why Trump fired former FBI Director James Comey and insisted his removal “simply has no relevance to the integrity of the Russian investigation as it moves ahead.”

But Barr told senators at his confirmation hearing that "it is vitally important" for Mueller's investigation to be completed, according to a transcript of his prepared remarks.

“I believe it is in the best interest of everyone – the President, Congress, and, most importantly, the American people – that this matter be resolved by allowing the Special Counsel to complete his work,” Barr said, according to the transcript. “The country needs a credible resolution of these issues. If confirmed, I will not permit partisan politics, personal interests, or any other improper consideration to interfere with this or any other investigation.”

He opposed Roe v. Wade

During the confirmation hearings when he was first appointed attorney general, Barr said he did not agree with the Supreme Court’s Roe v. Wade decision and viewed abortion as an issue best left to the states, the Los Angeles Times reported at the time.

He said he didn’t think the right to privacy “extends to abortion.”

His answer reportedly surprised then-Sen. Joe Biden, who said Barr should be “complimented” for his “candid answer,” even though the eventual U.S. vice president did not agree.

He worked for several corporations after his Justice Department career

From Verizon Communications to GTE Corporation, Barr spent more than 14 years working in senior corporate positions following his career at the Justice Department, according to his biography.

“At Verizon and GTE, [Barr] provided legal advice to senior management and the board of directors and led the legal, regulatory and government affairs activities of the companies,” his biography stated.

He also helped with mergers, including that of GTE and Bell Atlantic – thus creating Verizon.

Later, he advised corporations on regulatory litigation, according to his biography.

Barr is currently employed with the Kirkland & Ellis law firm in Washington, D.C. There, he still advises corporations with enforcement and regulatory issues, according to The Washington Post.

He worked in the CIA

Barr worked in the Central Intelligence Agency from 1973 until 1977 as an analyst and assistant legislative counsel, according to his Justice Department biography.

During this time, he studied law at night at George Washington University. He already received a bachelor’s degree in government and a master’s degree in government and Chinese studies – both from Columbia University.

Fox News' Andrew O'Reilly, Alex Pappas and John Roberts contributed to this report.