House Homeland Security Committee Chairman Mark Green, R-Texas, is calling on Secret Service Director Kim Cheatle, Secretary of Homeland Security Alejandro Mayorkas and FBI Director Christopher Wray to testify before the committee on Tuesday, July 23.

"The American people want answers," Green said in a statement. "It is imperative that we partner to understand what went wrong, and how Congress can work with the departments and agencies to ensure this never happens again."

Cheatle is expected to testify before the GOP-led House Oversight Committee on Monday, July 22.

One of the men injured in Saturday's shooting, 57-year-old David Dutch, was shot in the chest and liver, according to the Marine Corps League of Pennsylvania.

Dutch is no longer in a medically induced coma and has been upgraded from critical to stable condition, the organization said.

Dutch is a former Marine who serves as commandant of his Marine Corps League detachment, the organization said.

The other injured victim, 74-year-old James Copenhaver, has also been upgraded from critical to stable condition, officials said.

-ABC News’ Alex Presha

In a private phone call with Robert F. Kennedy Jr., former President Donald Trump said the bullet "sounded like the world’s largest mosquito."

RFK Jr.'s son posted on X a video of the call, which was filmed from what looks to be RFK Jr.'s hotel room. RFK Jr. had Trump on speaker phone.

The younger Kennedy, Bobby Kennedy III, removed the post after his father said on X that he was "mortified" it became public.

Trump also told RFK Jr. about the phone call he received from President Joe Biden after Saturday’s assassination attempt.

"It was very nice, actually. He called me, and he said, 'How did you choose to move to the right?' [Inaudible] Everybody’s looking straight on," Trump said. "I said, 'I was just showing a chart.'"

-ABC News’ Will McDuffie

The Department of Homeland Security and the FBI have issued a bulletin to law enforcement across the country warning them that, in the wake of Saturday's shooting, violent extremists could try to conduct "follow-on or retaliatory" attacks at events over the next few months related to the 2024 presidential election.

The bulletin urged local, state and federal law enforcement -- and their partners -- to remain vigilant and report any suspicious behavior.

The bulletin also said that "lone actors" or small groups of extremists "likely will continue to view" political rallies and campaign events as "attractive targets."

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