On Sunday night, minutes after Will Lewis, the chief executive of The Washington Post, informed employees that the newspaper’s executive editor, Sally Buzbee, was being replaced, managers gathered on a conference call to hear from their boss one last time.

Ms. Buzbee told them that a new organizational structure created by Mr. Lewis — effectively splitting the Washington Post newsroom and opinion section into three smaller divisions — didn’t work for her. She added that Mr. Lewis was pushing for aggressive moves to turn around The Post, and asked editors to reserve judgment for now.

“I would have preferred to stay to help us get through this period, but it just got to the point where it wasn’t possible,” Ms. Buzbee said, according to a person familiar with the matter.

The stunning call — which some attendees described as funereal — added to the growing tension between the newsroom and Mr. Lewis, who has set about remaking The Post since he started in January.

Many reporters and editors figured that Ms. Buzbee would remain in place until at least the presidential election in November. Just two weeks ago, Mr. Lewis and Ms. Buzbee had addressed The Post’s staff together at a long-awaited all-hands meeting.

But Ms. Buzbee chafed at Mr. Lewis’s plans to separate The Post’s newsroom into segments, according to two people familiar with her thinking, and the pair quickly reached an impasse. Mr. Lewis said she could run one of the two the newsroom segments, but she resigned instead, according to a person with knowledge of the interactions.