CAIRO — Over speakers, the news came Wednesday and some people fainted. An hour later it had settled in, and President Mohamed Morsi’s supporters sat dazed on sidewalks or walked home, glassy-eyed.

As he left the sit-in in front of Cairo University, Khaled Mohamed found himself suddenly, and painfully, facing Egypt’s new reality. In front of him were soldiers, and beyond them, people who seemed to revel in his misfortune. They celebrated Mr. Morsi’s fall and the dramatic eclipse of Mr. Mohamed’s 80-year-old organization, the Muslim Brotherhood.