US Secret Service Director Kimberly Cheatle resigned on Tuesday after outrage expressed by both political parties over her agency's failure to prevent an assassination attempt against former president Donald Trump at a campaign rally 10 days ago in Pennsylvania.

Cheatle, 53, announced her resignation through an internal email. She said that "in light of recent events, it is with a heavy heart that I have made the difficult decision to step down as your director". Cheatle said that she didn't want the calls for her resignation "to be a distraction from the great work" the agency is doing.

Cheatle served on the team of agents that secured Vice-President Dick Cheney on Sept. 11, 2001. Cheatle later worked on Joe Biden's detail during his vice-presidency and was assigned to his wife, Jill Biden.

President Biden issued a statement Tuesday after her resignation: "As a leader, it takes honor, courage and incredible integrity to take full responsibility for an organization tasked with one of the most challenging jobs in public service."

Within minutes after news of Cheatle's resignation broke, Trump posted a statement on his social media network saying: "The Biden/Harris Administration did not properly protect me, and I was forced to take a bullet for Democracy. IT WAS MY GREAT HONOR TO DO SO!"

Homeland Security Secretary Alejandro Mayorkas appointed Secret Service Deputy Director Ronald Rowe as the agency's acting director. Rowe is a 24-year veteran of the service. In an interview last week, Rowe defended Cheatle's leadership and said she shouldn't resign.

The security measure during Trump's July 13 rally was seriously flawed by not monitoring a nearby warehouse, where the gunman, Thomas Crooks, 20, positioned himself for the shooting.

The day before her resignation, Cheatle testified at a congressional hearing where she offered no clear answers to the failure to protect Trump.

She acknowledged that the shooter was identified as suspicious — having had a range finder and backpack — more than an hour before he opened fire. She also acknowledged that Secret Service agents had received multiple notifications of a person acting suspiciously "somewhere between two and five times" prior to the shooting.

However, the potential threat seemed to not have been conveyed to Trump's security team.

"If the detail had been passed information that there was a threat, the detail would never have brought the former president out on the stage," Cheatle said in the hearing.

Crooks fired at least six rounds from an AR-15-style rifle from the roof of the American Glass Research building, roughly 400 feet from where Trump spoke. The shots killed one spectator, critically injured two others and grazed Trump's right ear.

A Secret Service sniper team shot back, killing Crooks, whose motive remains unknown.

House Speaker Mike Johnson and House Minority Leader Hakeem Jeffries on Tuesday agreed to form a bipartisan task force to lead the congressional investigation into the assassination attempt.

"The security failures that allowed an assassination attempt on Donald Trump's life are shocking," Johnson and Jeffries said in a joint statement. "The task force will be empowered with subpoena authority and will move quickly to find the facts, ensure accountability, and make certain such failures never happen again."