Washington — The House Oversight and Accountability Committee's chairman plans to subpoena U.S. Secret Service Director Kimberly Cheatle for testimony on the assassination attempt against former President Donald Trump, a spokeswoman for the panel said Tuesday.

Cheatle is set to appear before committee members for an oversight hearing on July 22, Chairman James Comer, a Kentucky Republican, announced Monday. While the Secret Service also agreed to brief lawmakers on Tuesday, the panel's spokeswoman said, the Department of Homeland Security "took over communications" with the committee and has not confirmed a time for the briefing.

"The Oversight Committee has a long record of bipartisan oversight of the Secret Service and the unprofessionalism we are witnessing from current DHS leadership is unacceptable," the spokeswoman said. "While the Secret Service confirmed Director Cheatle is expected to appear for the committee's hearing on July 22, to head off any attempt by DHS to backtrack on her appearance, the chairman will issue a subpoena for her to attend. Director Cheatle must answer to Congress and the American people about the historic failure that occurred on her watch."

Cheatle's job at the helm of the Secret Service has come under scrutiny following the shooting at Trump's rally in Butler, Pennsylvania, on Saturday, during which the former president was injured when a bullet grazed his ear. One spectator, firefighter Corey Comperatore, was killed in the attack and two others, Marine Corps veteran David Dutch and James Copenhaver, were wounded.

The FBI identified Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania, as the gunman. He was killed by a Secret Service sniper. 

Questions quickly arose in the wake of the assassination attempt about how Crooks was able to gain access to a rooftop so close to where Trump was speaking to the crowd of supporters. President Biden said Sunday that he ordered an independent review of security at the rally and asked the Secret Service to review security measures for this week's Republican National Convention in Milwaukee.

Cheatle said Monday that the agency will "participate fully" in the review announced by Mr. Biden and is working with federal, state and local agencies to understand what happened at Trump's rally, how it occurred and how it can be prevented from taking place again.

The Secret Service chief said the agency provided additional security enhancements for Trump's detail in June and implemented changes to his security detail after the shooting to ensure continued protection for the convention and rest of the campaign.

The House and Senate Homeland Security Committees have said they will also be looking into the shooting. The head of the House Homeland Security Panel, Rep. Mark Green, invited Homeland Security Secretary Alejandro Mayorkas, FBI Director Chris Wray and Cheatle to testify before lawmakers next Tuesday to examine the circumstances surrounding the attack.

Michael Kaplan contributed to this report