Washington (CNN) By choosing Robert S. Mueller III for the job of special counsel, Deputy Attorney General Rod Rosenstein tapped a veteran of the law -- a seasoned prosecutor, former FBI director and private lawyer -- who will methodically peel back the layers of the investigation into Russian interference in the 2016 presidential campaign.

Any other prosecutor might think twice before taking on a job so fraught with political controversy.

But as a stunned Washington digested Wednesday's surprise announcement, Mueller released a terse statement at 7:04 p.m. ET Wednesday night acknowledging that he would "accept the responsibility" and "discharge it to the best of my ability."

And then he got to work.

By 7:38 p.m. ET, his now former firm, WilmerHale, announced that two other partners had stepped down to help -- including one who worked for the Watergate prosecutor back in the 1970s.

"Bob Mueller's attributes are legion," said Richard Ben-Veniste, who served as a special prosecutor during the Watergate scandal and knows the new special counsel.

Mueller's process

Mueller will start with reviewing existing files and talking to the agents who have been on the case. Then he will collect facts and piece together the time line as he sets his investigative strategy. There could be a variety of records, emails, texts, and maybe even recordings.

If past is precedent, he will work his way up to those who are more centrally involved, something that could take months and leave the Trump administration under somewhat of a shadow.

"He will have the opportunity to interview witnesses at a pace he decides is appropriate and, if necessary, he will have the power to immunize witnesses and present evidence to a grand jury," Ben-Veniste said.

Although Mueller has spent stints of his career in private practice, his passion -- according to friends -- has been for public service. His career path has been unusual. After serving as head of the criminal division at the Justice Department, he joined a law firm in DC. But then he gave up a lucrative partnership to take a job as a line prosecutor in the homicide division of the US Attorney's Office.

"He's prosecuted everything from drug-related murders on DC streets to international terrorism in the skies over Lockerbie," said attorney Neil H. MacBride of the law firm Davis Polk, who has known and worked with Mueller for over 20 years.

"Bob used to tell young prosecutors and agents that integrity is doing the right thing when no one else is watching you," MacBride said.

Mueller's work ethic is legendary.

"He's the first person in and the last person out, that's the reason everyone claims he is the gold standard," said longtime friend Daniel Levin of the law firm White & Case. Levin says he brings to the job a terrific judgment when it comes to the criminal justice system and a "very good sense of how things work."

For Levin the most important quality is that after a long stellar career the most remarkable thing is that he "has no ego."

"He's really not looking to make himself good. He will get to the right result, whatever it is," he said.

And for a city that floats on leaks, Mueller will turn off the spigot.

His staff

The two men whom he brings with him bring different qualities.

Aaron Zebley was Mueller's chief of staff at the FBI. He also worked as the senior counselor in the National Security Division and knows his way around the Justice Department. Zebley earned his law degree in 1996 from the University of Virginia School of Law and an undergraduate degree from the College of William and Mary.

James Quarles has spent the last several years at a private firm focusing on complex litigation matters and management, but it's how his career started that might prove critical. Like Ben-Veniste, Quarles worked on the Watergate Special Prosecution Force, for which he served as an assistant special prosecutor.

"There is nothing comparable to the kind of pressure and obligation that this kind of job puts on your shoulders," said Ben-Veniste. "Having been there before, gives him the confidence to know how to do it and how to do it right."