WASHINGTON ― Kimberly Cheatle, director of the U.S. Secret Service, acknowledged Monday that the near-assassination of former President Donald Trump represented a fundamental failure on her agency’s part, but refused to explain exactly what went wrong.

Speaking before lawmakers on Capitol Hill, Cheatle described the July 13 shooting of Trump and attendees at his rally in Butler, Pennsylvania, as “the most significant operational failure” at the Secret Service in decades.

“The Secret Service’s solemn mission is to protect our nation’s leaders,” Cheatle said in an opening statement before the House oversight committee. “On July 13th, we failed.”

Cheatle said she took “full responsibility for any security lapse” by her agency, though she has rebuffed calls for her resignation from oversight chair Rep. James Comer (R-Ky.) and other Republicans.

And for the most part, Cheatle refused to answer specific questions about the Secret Service’s planning for the 13th, instead speaking in generalities about how the agency operates. Cheatle said she would defer to the multiple ongoing investigations of the failure, including the FBI’s criminal investigation into the shooting.

“I’m not going to get into the specifics of that day itself,” Cheatle told Comer, prompting a disgusted reaction from Rep. Marjorie Taylor Greene (R-Ga.) and other Republicans in the room.

But there was one major exception to Cheatle’s stonewalling: She denied that the Secret Service had turned down requests from the Trump campaign for extra security measures.

“There were no assets denied for that event in Butler on the 13th,” Cheatle said.

The Washington Post reported over the weekend that the agency had previously denied requests for extra security at other public appearances by the former president.

When Rep. Jim Jordan (R-Ohio) asked Cheatle about past denials for more security, she wouldn’t go into detail.

“Looks like you won’t answer some pretty basic questions,” Jordan said.

Asked about reports that the Secret Service had flagged the shooter well before Trump took the stage, Cheatle said they may have thought he was suspicious, but didn’t know he was a threat. “The detail would never have brought the former president out on stage” if they’d known there was a threat, she said.

Comer asked Cheatle if the Secret Service had ever placed an agent on the roof from which Thomas Crooks fired multiple rounds from a high-powered rifle, killing former fire chief Corey Comperatore and wounding several others, including Trump. He asked if the Secret Service used a drone to surveil the scene. Cheatle wouldn’t say.

Comer and the committee’s top Democrat, Rep. Jamie Raskin (D-Md.), jointly demanded that Cheatle testify, and Comer reinforced that demand with a subpoena. The skepticism toward Cheatle on Monday was remarkably bipartisan, though with differences of emphasis, as several Democrats, including Raskin, tied the Butler shooting to the broader problem of gun violence in the U.S.

“Since the mass shooting in Butler, there have already been at least 10 additional mass shootings in the United States,” Raskin said.

Comer repeated his call for Cheatle to step down, and Rep. Mike Turner (R-Ohio) said that if she wouldn’t do so, then President Joe Biden should fire her.

“The Secret Service has thousands of employees and a significant budget, but it has now become the face of incompetence,” Comer said. “It is my firm belief, Director Cheatle, that you should resign.”