WASHINGTON (AP) — The Republican chairman of the House Oversight and Accountability Committee issued a subpoena Wednesday to Secret Service Director Kimberly Cheatle compelling her to appear before the committee on Monday for what is scheduled to be the first congressional hearing into the attempted assassination of former President Donald Trump.

Rep. James Comer said initially that the Secret Service committed to her attendance but that Homeland Security officials appear to have intervened and there has been no "meaningful updates or information" shared with the committee.

Comer said the "lack of transparency and failure to cooperate" with the committee called into question Cheatle's ability to lead the Secret Service and necessitates the subpoena.

Cheatle has said the agency understands the importance of a review ordered by Democratic President Joe Biden and would fully participate in it as well as with congressional committees looking into the shooting.

"The assassination attempt of the former President and current Republican nominee for president represents a total failure of the agency's core mission and demands Congressional oversight," Comer wrote in a letter to Cheatle.

The subpoena was just one of a series of developments that occurred Wednesday in the wake of the Saturday assassination attempt.

The fact that a shooter was able to get so close to the former president while he's supposed to be closely guarded has raised questions about what security plans the agency tasked with taking a bullet for its protectees put in place and who is ultimately responsible for allowing the 20-year-old gunman to climb a roof where he had a clear line of sight to a former president.

Earlier, House Speaker Mike Johnson announced he would be setting up a task force to investigate security failures that occurred during the assassination attempt. He also said he would be calling on Cheatle to resign from her post as director of the Secret Service, saying on Fox News Channel without elaborating, "I think she's shown what her priorities are."

He said the task force would be made up of Republicans and Democrats and its formation would speed up the investigative process.

"There's not a lot of the procedural hurdles, and we'll have subpoena authority for that task force as well," Johnson said.

Johnson said he has not received satisfactory answers from Homeland Security Secretary Alejandro Mayorkas or leaders at the FBI.

"We must have accountability for this. It was inexcusable," Johnson said. "Obviously, there were security lapses. You don't have to be a special ops expert to understand that. And we're going to get down to the bottom of it quickly."

The Department of Homeland Security did not respond to requests for comment on the subpoena.

Cheatle said during an interview Monday with ABC News that the shooting should never have happened, but also said she has no plans to resign.

When asked who beares the most responsibility for the shooting happening, she said: "What I would say is the Secret Service is responsible for the protection of the former president."

"The buck stops with me. I am the director of the Secret Service," she said.

So far, she has the support of the administration.

"I have 100% confidence in the director of the United States Secret Service. I have 100% confidence in the United States Secret Service," Homeland Security Secretary Alejandro Mayorkas said Monday.

But in addition to the Congressional inquiries, Cheatle and the Secret Service are also facing an inquiry by the Department of Homeland Security's inspector general.

In a brief notice posted to the inspector general's website Tuesday, the agency said the objective of the probe is to "Evaluate the United States Secret Service's (Secret Service) process for securing former President Trump's July 13, 2024 campaign event."

The agency also said Wednesday that it is launching a review of the agency's Counter Sniper Team's "preparedness and operations."

"Our objective is to determine the extent to which the Secret Service Counter Sniper Team is prepared for, and responds to, threats at events attended by designated protectees," the inspector general's office said.

Biden on Sunday said he was ordering an independent review of the security at the rally. No one has yet been named to lead that inquiry.

Since the shooting, Cheatle and the Security Service have come under intense scrutiny over how a gunman could get in position to fire at a former president.

The shooter, Thomas Matthew Crooks, was able to get within 135 meters (157 yards) of the stage where the Republican former president was speaking when he opened fire. That's despite a threat on Trump's life from Iran leading to additional security for the former president in the days before the Saturday rally.

A bloodied Trump was quickly escorted off the stage by Secret Service agents, and agency snipers killed the shooter. Trump said the upper part of his right ear was pierced in the shooting. One rallygoer was killed, and two others critically wounded.

Cheatle said her agency was working to understand how Saturday's shooting happened and to make sure something like it never does again.

The agency of roughly 7,800 staff members is responsible for protecting presidents, vice presidents, their families, former presidents, their spouses and their minor children under the age of 16 and a few other high-level Cabinet officials such as the Homeland Security secretary.