WASHINGTON — FBI Director James Comey’s announcement that his bureau was reviewing new emails possibly relevant to Hillary Clinton’s private email server investigation has thrust him into the public spotlight again just days before Election Day.

Comey said in a letter Friday to Congress the FBI uncovered email messages in an unrelated case and would determine if they were classified. The surprise disclosure was seized upon by eager Republicans while drawing criticism from Clinton supporters, who said the lack of detail could unfairly sway the presidential election.

Comey acknowledged later he faced a “significant risk of being misunderstood.” He told FBI employees the bureau did not yet know the significance of the emails but he felt obligated to disclose the information.

The 55-year-old former Republican was nominated by President Obama for the FBI post in 2013. Praised for his independence and integrity, Comey has spent three decades in law enforcement and has been no stranger to controversy.

Some career highlights:

Opposed secret spy program

Comey is perhaps best known for a remarkable 2004 standoff with top officials in the George W. Bush administration. He rushed to the hospital bed of Attorney General John Ashcroft to physically stop White House officials in their bid to get his ailing boss to reauthorize a secret no-warrant wiretapping program.

Publicly disagreed with Obama administration

Comey irritated Obama officials after he suggested last year that increases in violent crime across the country could be fueled in part by anxiety among law enforcement officers who increasingly fear being recorded by citizens.

Angered tech industry

As the public face of the federal government, Comey went to court earlier this year to force Apple Inc. to help it open the locked iPhone of Sand Bernardino shooter Syed Farook. After the California attack last December, which killed 14 people. Farook and his wife died in a gun battle with police.

Clinton emails Part One

Comey announced in July that the FBI was recommending no criminal charges for Clinton’s handling of highly classified material in a private email account. That drew the dismay of Republicans in an election year.