Kimberly Cheatle - the head of the United States Secret Service - has resigned amidst mounting pressure following an assassination attempt on former President Donald Trump.

The incident, which took place at a rally in Pennsylvania on July 13, has raised serious concerns about security protocols and the effectiveness of the Secret Service.

Cheatle informed her staff of her decision to step down in an email sent on Tuesday. “I take full responsibility for the security lapse,” Cheatle wrote. “In light of recent events, it is with a heavy heart that I have made the difficult decision to step down as your director.”

The resignation follows intense scrutiny from US lawmakers, who have been questioning the adequacy of the security measures in place at the rally where Trump, the Republican presidential nominee, was shot in the ear by a gunman.

Witnesses reported that the assailant had a clear line of sight from a rooftop, prompting further questions about the pre-event security checks.

During a congressional hearing on Monday, Cheatle faced stern inquiries regarding the Secret Service’s operational failures.

“The assassination attempt on former President Donald Trump on July 13 is the most significant operational failure at the Secret Service in decades,” Cheatle admitted to lawmakers. “There clearly was a mistake and we will make every effort to make sure that this never happens again.”

The fallout from the incident has led to an independent review of the security protocols by order of President Joe Biden. The review comes in the wake of not only the shooting of Trump but also the death of one rally attendee and serious injuries to two others. President Biden, in a statement following Cheatle’s resignation, thanked her for her decades of public service and indicated that he would soon appoint her replacement.

“The independent review to get to the bottom of what happened on July 13 continues, and I look forward to assessing its conclusions. We all know what happened that day can never happen again,” Biden said.

Republican House Speaker Mike Johnson expressed that Cheatle’s resignation was a necessary step. “Now we have to pick up the pieces; we have to rebuild the American peoples’ trust and trust in the Secret Service as an agency. It has an incredibly important responsibility in protecting presidents, former presidents, and other officials in the executive branch,” Johnson said.

The resignation comes at a crucial time as the United States gears up for the upcoming election in November. Former President Trump is set to face Democratic Vice President Kamala Harris in the race, following Biden’s recent withdrawal.

Al Jazeera’s Mike Hanna highlighted the significance of the timing, noting that the new Secret Service director will have a critical role during the politically charged period.