The director of the U.S. Secret Service took responsibility for staggering security lapses ahead of the assassination attempt on former U.S. president Donald Trump, but declined to answer questions directly, prompting frustrated lawmakers from both sides of the aisle to demand she step down.

Kimberly Cheatle, who resisted the calls to resign, told the House oversight committee on Monday that the shooting was the “most serious operational failure” by the Secret Service in more than four decades.

“The Secret Service’s solemn mission is to protect our nation’s leaders. On July 13th, we failed. As the director of the United States Secret Service, I take full responsibility for any security lapse”, Cheatle said, speaking in Washington, D.C., under subpoena.

The shooting at a rally in Butler, Pa., injured Trump’s right ear, killed a local firefighter and injured two more attendees. Cheatle was hammered Monday with more than four hours of intense questioning focused on two blunt themes: how an attempt on the life of a former president and current candidate happened under her watch and whether she should keep her job.