Whatever secrets Hillary Clinton had on her email system, they’re now possibly in the hands of hackers, FBI director Jim Comey said in an extraordinary press conference.

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.