Kimberly Cheatle, the director of the Secret Service, announced her resignation today after acknowledging that her agency had failed to adequately protect Donald Trump from an attempted assassination earlier this month.

Her decision to step down was a rapid fall after nearly 30 years in the agency. But her departure had become increasingly expected over the past week, especially after lawmakers in both parties called for her to resign during a contentious hearing yesterday on Capitol Hill.

“I was surprised that it took this long,” said my colleague David Fahrenthold, who has been reporting on the shooting, which occurred at a Trump rally in Butler, Pa., on July 13.

The top Republican and Democrat in the House said today that they were forming a bipartisan task force to investigate the shooting. When I asked David about the big questions still remaining, he said there were many:

There are still not complete answers for why the roof used by the shooter was left unsecured; how the gunman was able to elude police after he was labeled a “suspicious person”; and why agents near Trump were not informed of reports of a man crawling on the roof. There are also several unanswered questions about the gunman himself and his motives.

“It’s clear that the job of the Secret Service is harder than it used to be. They protect more people now than they used to, especially during campaign season, and it’s clear that their resources were stretched,” David told me. “But the problems in Butler went beyond the budget — there was a lack of imagination and of clear accountability.”

Visual investigation: The Times recreated, in 3-D, the lines of sight for three countersniper teams and the would-be assassin, showing how he had an advantage over law enforcement officers.