But if firing Mr. Comey was meant to help restore the bureau’s credibility and put the work force at ease about the F.B.I.’s future, as Justice Department officials said, it has had the opposite effect.

“People are stunned right now,” said Frank Montoya Jr., a former senior F.B.I. official. An F.B.I. spokesman declined to comment about bureau morale.

For the moment, the bureau is being run by Andrew G. McCabe, a veteran F.B.I. agent and previous deputy director who was at Mr. Comey’s side as he navigated the politically perilous currents of the Clinton and Russia investigations that ultimately brought him down. Mr. McCabe held conference calls with the F.B.I.’s top agents late Tuesday and on Wednesday and told them to stay focused on their work. It was to be business as usual, he said.

It is not clear whether Mr. McCabe will stay on as acting director. He is under consideration for the role of interim director, who will stay in place until Mr. Trump’s eventual nominee is confirmed by the Senate, the Justice Department official said.

The four candidates being interviewed Wednesday for the interim role were William Evanina, the director of the National Counterintelligence and Security Center at the Office of the Director of National Intelligence; Paul Abbate, assistant director of the F.B.I.’s Criminal, Cyber, Response and Services Branch; and Michael J. Anderson and Adam Lee, who run the Chicago and Richmond, Va., field offices, respectively.

The official cautioned that the list was not exhaustive.

Whatever happens, another senior F.B.I. official said stoically, the bureau will continue to investigate crimes. The day Mr. Comey was fired was no different from the day before, the official insisted.