FBI Director James Comey shattered precedent when he publicly announced in July that, while Hillary Clinton's handling of classified email communications as secretary of state was "extremely careless," he saw no basis for criminal charges.

But he shattered precedent again Friday by announcing, just days before voters go to the polls in a bitterly contested presidential election, that the bureau would be examining thousands more emails that recently came into the possession of the FBI.

That latest decision has roiled the presidential campaign and raised questions anew about Comey's tactics and underlying aims. Veteran former prosecutors say they cannot recall another instance in which an FBI director has come forward to publicly explain the details of a criminal investigation as it was being closed. Nor can they recall an instance in which the FBI has publicly disclosed new investigative steps related to a prominent politician within days of an election.

"It was highly unusual from the very beginning," said Robert Leight of Pittsburgh, a lawyer with Pietragallo Gordon Alfano Bosick & Raspanti. Leight served from 1982 through 1989 as an FBI agent specializing in organized crime and narcotics investigations and later as an assistant U.S. attorney. "I have never seen the FBI make a statement publicly that they were not going to recommend a prosecution."

Leight, who remains in touch with former FBI colleagues, said the consensus is that Comey has handled the matter poorly.

Clinton, saying she is confident the investigation will show she has done nothing wrong, has called on Comey to release what he has. Meantime, Justice Department officials said Comey's announcement, in a letter to congressional leaders, breached a long-standing Justice Department practice barring public commentary on ongoing criminal investigations, or actions that might tip elections, shortly before voters go to the polls.

Comey, a former Republican appointed by President Obama in 2013, announced July 1 that his agency would recommend against prosecuting Clinton for storing classified information on a private server not subject to government security measures, a felony offense.

But then in another highly unusual move he disclosed Friday that the FBI was taking new action based on thousands of emails that he said "appear to be pertinent to the investigation." He also said the FBI "cannot yet assess whether or not this material may be significant."

Reports have said the emails were found on a laptop computer shared by former Rep. Anthony Weiner (D., N.Y.) and his wife, Huma Abedin, a senior Clinton adviser and confidante. Weiner is reportedly under investigation in a separate probe for allegedly sending sexually suggestive emails to a minor.

Clinton has said that she turned over more than 30,000 work-related emails to the State Department after leaving office, which in turn has turned them over to the FBI. At the same time, Clinton's lawyers destroyed 30,000-plus emails that were stored on her private server in the basement of her home in Chappaqua, N.Y., that were deemed to be nonwork-related. It is not known whether the emails to be scrutinized by the FBI contain classified information or whether they are among the emails deleted initially by Clinton's lawyers.

"This is terra incognita," said L. George Parry, a former city and federal prosecutor now in private practice with the Philadelphia firm of Davis, Parry & Tyler P.C. "I have never seen the FBI director hold a press conference to announce [he would not prosecute]."

Parry is sharply critical of Comey for not bringing criminal charges the first time around and he said Friday's announcement won't repair the damage.

"Whether Comey thinks he is saving face or bringing back some credibility to the FBI, I couldn't tell you," Parry said. "Whatever he is trying, it is not going to work."

At different times, Comey has come under withering criticism from various points on the political spectrum. Republicans question his decision recommending against the prosecution of Clinton and offering key figures in the investigation immunity deals without getting much in return. Democrats have been hammering Comey since his Friday announcement, saying it was unfair and improper to announce the investigative action so close to the election without providing any details or giving Clinton the opportunity to respond.

The criticism that has emerged since Comey's July announcement that he would recommend against criminal charges has centered, in part, on the highly unusual nature of the criminal probe, details of which have been dribbling out. No grand jury was impaneled to hear evidence; many, if not most, of the key players in the probe were given immunity and the FBI agreed to destroy laptops that it had obtained from Clinton aides Cheryl Mills and Heather Samuelson at the conclusion of the probe.

Democrats, meantime, have been pounding Comey for going public with word of the investigation. At the same time, former Justice Department spokesman Matthew Miller said in a series of tweets that Comey's announcement was "such an inappropriate disclosure."

"I have yet to hear from a single former prosecutor who agrees with what he did," Miller said.