Ever since Hillary Clinton’s private email system was exposed, Republicans have accused her of jeopardizing U.S. national security by exposing classified information to Russian, Chinese, and other foreign hackers. In extraordinary public statement on Tuesday, FBI Director James Comey all but confirmed the line of attack used by Clinton’s critics, saying “it is possible” her system was breached.

Comey spoke to reporters from FBI headquarters, where he announced that the bureau would not recommend seeking a criminal indictment against Clinton for using a private email system, which he said was used to send and receive highly classified information.

But he chastised Clinton’s decision as “extremely careless” and laid out different ways that her account may have been compromised.

Comey said that even though investigators had found no “direct evidence” of a breach by a foreign power or other “hostile actors,” the FBI “would be unlikely to see such evidence” given the “nature of the system,” which he described as a “complicated” mix of servers and mobile devices managed by different administrators. He likened the challenge that forensic investigators faced when examining one of those servers, which was decommissioned in 2013, to “removing the frame from a huge finished jigsaw puzzle and dumping the pieces on the floor.”

Comey went on to note that people in “regular contact” with Clinton via her personal email had themselves been hacked; that Clinton’s use of a personal account was “both known by a large number of people and readily apparent;” and that she “used her personal email extensively while outside the United States, including sending and receiving work-related emails in the territory of sophisticated adversaries.”

Putting all those factors together, Comey said, “we assess it is possible that hostile actors gained access to Secretary Clinton’s personal email account.”

Donald Trump, Clinton’s opponent for president, tweeted that Comey “said Crooked Hillary compromised our national security” and seemed to criticize the FBI’s decision not to recommend a criminal prosecution. Trump had previously said that Clinton was unqualified to run for president because of the email scandal and that she should leave the race.

It had previously been reported that some of Clinton’s emails contained conversations about U.S. drone strikes. But senior officials are also targeted for more mundane information, including policy positions, speeches, and negotiating strategies, that can give useful insights into U.S. foreign policy and national security strategy. Comey gave no indication as to the subject of the information in Clinton’s emails that was deemed classified.

Comey’s statement baffled some observers, who questioned by the FBI director would wade into a political controversy at the heart of the presidential election.

“Since when does the FBI director publicly speculate about things that aren’t supported by evidence?” Matthew Miller, the former spokesperson for Attorney General Eric Holder, told The Daily Beast.

Miller called Comey’s decision to speak about the FBI’s findings and its recommendation to Justice Department prosecutors not to charge Clinton “absolutely unprecedented in terms of the process that the FBI director is supposed to follow in these cases.”

Comey, who also served as deputy attorney general in the George W. Bush administration, acknowledged at the outset it was “unusual” for the FBI director to talk about the process of a criminal investigation as well as conversations with prosecutors.

“I think the American people deserve those details in a case of intense public interest,” Comey said, adding, “I have not coordinated or reviewed this statement in any way with the Department of Justice or any other part of the government.”

Some also questioned whether Clinton had been given special treatment owing to her political-celebrity status.

“If that had been me, they would have pulled my clearance right away,” one Pentagon official said.

Throughout the U.S. military, where nearly everyone is aware of the rules that come with holding a clearance, many noted that a different standard seemed to have been applied to Clinton. Retired Gen. David Petraeus pleaded guilty to a misdemeanor charge for improperly sharing classified information. And former soldiers have been prosecuted or sanctioned for writing writing tell-all books without properly vetting them with the government.

Almost immediately, Republicans seized on Comey’s comments, which included the FBI’s finding that 110 emails from the 30,000 Clinton turned over to the State Department as being business-related contained “classified information at the time they were sent or received,” including seven “email chains” that concerned matters at the top secret/special access program level, effectively the nation’s most closely guarded secrets.

“The FBI’s findings are a glaring indictment of Hillary Clinton’s complete lack of judgment, honesty, and preparedness to be our next commander-in-chief,” Republican National Committee Chairman Reince Priebus said in a statement. “We now know...that her server was less secure than Gmail and was likely hacked by hostile actors.”

The notion that Clinton’s email was hacked is not far-fetched. Security experts have warned for months that her so-called homebrew system of servers based out of her home in New York made her a more vulnerable target.

Comey didn’t name the “territory of sophisticated adversaries” where Clinton had sent and received email on her personal devices, Clinton traveled to China seven times and to Russia four times as secretary of state, according to State Department records. Those countries are in the top-tier of U.S. adversaries targeting government personnel and have on various occasions successfully breached the computer networks of the White House, the State Department, and the Pentagon, according to U.S. officials and security experts.

And last summer, Obama administration officials concluded that China was behind a massive breach at the Office of Personnel Management that compromised sensitive personal details on millions of government employees.

—with additional reporting by Nancy A. Youssef