House Oversight Committee Chairman James Comer, R-Tenn., said Secret Service Director Kim Cheatle’s resignation is "a step toward accountability," but a "full review" is still needed "of how these security failures happened so that we can prevent them going forward."

"We will continue our oversight of the Secret Service in support of the House Task Force to deliver transparency, accountability, and solutions to ensure this never happens again," Comer said.

President Joe Biden said in a statement, "Jill and I are grateful to Director Kim Cheatle for her decades of public service. She has selflessly dedicated and risked her life to protect our nation throughout her career in the United States Secret Service."

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

Biden said he will appoint a new director "soon."

6:07

Embattled Secret Service Director Kim Cheatle resigns

On Monday, Cheatle told Congress that the attempted assassination against former President Donald Trump was the "most significant operational failure at the Secret Service in decades."

House Speaker Mike Johnson called the resignation "overdue."

"We need the Secret Service to be acting -- to be performing -- at the top of their game, and we'll ensure that that happens. I hope that the interim director or whomever is appointed to replace Director Cheatle will be very sober minded about the responsibility and take into account the very dangerous times in which we live," Johnson said.

-ABC News’ John Parkinson

Secret Service Director Kim Cheatle has resigned, according to two sources familiar with the decision.

In the days since the attack, Cheatle and the Secret Service have faced heightened scrutiny for failing to prevent the incident from happening.

Cheatle faced calls to resign from Republicans and Democrats.

"The Secret Service’s solemn mission is to protect our nation’s leaders and financial infrastructure. On July 13th, we fell short on that mission," Cheatle said in a letter to Secret Service employees, obtained by ABC News. "The scrutiny over the last week has been intense and will continue to remain as our operational tempo increases. As your Director, I take full responsibility for the security lapse."

"The Secret Service will move forward with our investigatory and protective mission in a steadfast manner. We do not retreat from challenge. However, I do not want my calls for resignation to be a distraction from the great work each and every one of you do towards our vital mission," Cheatle said, in part. "In light of recent events, it is with a heavy heart that, I have made the difficult decision to step down as your Director."

-ABC News' Luke Barr

Seven Republicans and six Democrats will be on the House task force investigating the Trump rally shooting, House Speaker Mike Johnson and House Minority Leader Hakeem Jeffries said.

The House is expected to vote on a resolution this week to establish the task force and its members.

"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," Johnson and Jeffries said in a statement Tuesday.

-ABC News’ Lauren Peller

Sen. Josh Hawley, R-Mo., said Monday that a whistleblower had come forward to his office claiming there was supposed to be a security officer posted on the roof of the building where the gunman fired from, but that that person abandoned the post due to the heat.

The whistleblower, who Hawley said has direct knowledge of the Secret Service's planning for the event, alleged "that there was supposed to be a law enforcement presence on the roof that day," Hawley wrote in a letter to Department of Homeland Security Secretary Alejandro Mayorkas posted on X. "In fact, the whistleblower alleges that at least one individual was specifically assigned to the roof for the duration of the rally, but this person abandoned his or her post due to the hot weather."

Hawley said the whistleblower also alleged that "concerns over the heat prompted law enforcement to forego patrolling" the building and instead station security personnel inside it.

Hawley's letter requests that Mayorkas address the whistleblower's allegations by Friday.

ABC News has reached out to the Secret Service for comment on the letter.

During a hearing before the House Oversight Committee on Monday, Secret Service Director Kim Cheatle said that there was "overwatch" provided for the roof, but did not elaborate, when asked why no agents were placed on the building.

"What I can tell you is that there was a plan in place to provide overwatch, and we are still looking into responsibilities and who was going to provide overwatch," Cheatle said. "But the Secret Service in general, not speaking specifically to this incident, when we are providing overwatch, whether that be through counter-snipers or other technology, prefer to have sterile rooftops."

-ABC News' Allison Pecorin