– Paul Manafort was in bed early one morning in July when federal agents bearing a search warrant picked the lock on his front door and raided his Virginia home. They took binders stuffed with documents and copied his computer files, looking for evidence that Manafort, President Donald Trump’s former campaign chairman, set up secret offshore bank accounts. They even photographed the expensive suits in his closet.

The special counsel, Robert Mueller, then followed the house search with a warning: His prosecutors told Manafort they planned to indict him, said two people close to the investigation.

The moves against Manafort are just a glimpse of the aggressive tactics used by Mueller and his team of prosecutors in the four months since taking over the Justice Department’s investigation into Russia’s attempts to disrupt last year’s election, according to lawyers, witnesses and U.S. officials who have described the approach. Dispensing with the plodding pace typical of many white-collar investigations, Mueller’s team has used what some describe as shock-and-awe tactics to intimidate witnesses and potential targets of the inquiry.

Mueller has obtained a flurry of subpoenas to compel witnesses to testify before a grand jury, lawyers and witnesses say, sometimes before his prosecutors have taken the customary first step of interviewing them. One witness was called before the grand jury less than a month after his name surfaced in news accounts.

The special counsel even took the unusual step of obtaining a subpoena for one of Manafort’s former lawyers, claiming an exception to the rule that shields attorney-client discussions from scrutiny.

“They are setting a tone. It’s important early on to strike terror in the hearts of people in Washington, or else you will be rolled,” said Solomon L. Wisenberg, who was deputy independent counsel in the investigation that led to the impeachment trial of President Bill Clinton in 1999. “You want people saying to themselves, ‘Man, I had better tell these guys the truth.’ ”

A spokesman for Mueller declined to comment. Lawyers and a spokesman for Manafort also declined to comment.

Few people can upend Washington like a federal prosecutor rooting around a presidential administration, and Mueller, a former FBI director, is known to dislike meandering investigations that languish for years. At the same time, he appears to be taking a broad view of his mandate: examining not just the Russian disruption campaign and whether any of Trump’s associates assisted in the effort, but also any financial entanglements with Russians going back several years. He is also investigating whether Trump tried to obstruct justice when he fired James Comey, the FBI director.

Manafort is under investigation for possible violations of tax laws, money-laundering prohibitions and requirements to disclose foreign lobbying. Michael Flynn, the former national security adviser, is being scrutinized for foreign lobbying work as well as for conversations he had last year with Russia’s ambassador to the United States. On Monday, Flynn’s siblings announced the creation of a legal-defense fund to help cover their brother’s “enormous” legal fees.

Mueller took over the Russia investigation in May, after the FBI had already spent nearly a year looking into connections between Trump’s associates and Russians.

Some lawyers defending people who have been caught up in Mueller’s investigation privately complain that the special counsel’s team is unwilling to engage in the usual back-and-forth that precedes — or substitutes for — grand jury testimony. They argue that the team’s more aggressive tactics might end up being counterproductive, especially if some grand jury witnesses turn out to be more guarded than they would have been in a more informal setting or invoke the Fifth Amendment.

To a degree, Mueller is in a race against three congressional committees that are interviewing some of same people who are of interest to the special prosecutor’s team.

Even if the committees refuse to grant them immunity, congressional testimony that becomes public can give other witnesses a chance to line up their stories.

Mueller’s need to navigate this complex landscape could explain the timing of the raid on Manafort’s house, which took place in the early hours of July 26.

The raid came one day after Manafort was interviewed by staff members of the Senate Intelligence Committee.