In the summer of 2022, Kimberly A. Cheatle, who handled global security at PepsiCo, delivered surprising news shortly before a board of directors meeting, according to a colleague at the time: President Biden had asked her to run the Secret Service.

The opportunity to return to an agency she had served for a quarter century was one she could not resist, the colleague recalled Ms. Cheatle saying.

She was sworn in that September. Now, less than two years later, an assassination attempt on former President Donald J. Trump has thrown her tenure into uncertainty.

Since a gunman’s bullet grazed Mr. Trump’s ear at a campaign rally on Saturday, Ms. Cheatle has been forced into an uncomfortable limelight. Critics have questioned how the agency could have missed a man with a gun on a rooftop less than 500 feet from the former president — especially when law enforcement was amassed just below.

An influential congressional panel will press Ms. Cheatle for answers at a public hearing next week on the first shooting of a current or former American president since 1981.

On Wednesday night, two Republican senators, John Barrasso of Wyoming and Marsha Blackburn of Tennessee, personally confronted Ms. Cheatle in a suite at the Republican National Convention, where she is the senior security official. When she attempted to leave, they followed her down a corridor and up a flight of stairs yelling questions that she did not answer.