Secretary of Homeland Security Alejandro Mayorkas said he’s appointed Secret Service Deputy Director Ron Rowe to serve as acting director of the agency.

"A 24-year veteran of the Secret Service, he previously served as the agency’s Assistant Director for the Office of Intergovernmental and Legislative Affairs, Deputy Assistant Director for the Office of Protective Operations, and in other leadership positions," Mayorkas said in a statement. "I appreciate his willingness to lead the Secret Service at this incredibly challenging moment, as the agency works to get to the bottom of exactly what happened on July 13 and cooperate with ongoing investigations and Congressional oversight."

The Pennsylvania State Police has interviewed 100 people and gathered 1,000 pieces of evidence in the investigation into the homicide of Corey Comperatore and the two others injured in the shooting, Pennsylvania State Police Col. Christopher Paris told the House Homeland Security Committee on Tuesday. The state police is also investigating the U.S. Secret Service counter sniper who shot the gunman as an officer-involved shooting.

Paris said the state police had two main responsibilities: to assist the Secret Service with the motorcade and staff security posts within the secure perimeter.

The state police had 32 troopers staffed for the July 13 rally, he said.

Paris said the Secret Service notified the state police about the rally on July 5.

An initial planning meeting with law enforcement agencies was held on July 8. State police participated in a walk-through at the Butler Farm Show Grounds on July 11.

The state police said it provided all resources requested by the Secret Service.

-ABC News’ Luke Barr and Mike Levine

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