FBI Deputy Director Paul Abbate revealed Tuesday that federal investigators do not have complete access to emails that former President Trump's shooter, Thomas Matthew Crooks, sent.

"I think we've experienced a range of returns because some of the applications that he was using online were encrypted in nature," Abbate said while testifying before members of the Senate Homeland Security Committee and Judiciary Committee.

"Some of the email accounts will be broken into them. There are some that we have not been able to get information back because of their encrypted nature," he said.

Abbate's admission that the FBI does not have a complete handle on the information on Crooks' cellphone came after Sen. Lindsey Graham, R-S.C., a ranking member on the Senate Judiciary Committee, asked about the 20-year-old's electronics that were obtained by the federal agency.

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Ronald Rowe Jr. (left) speaks with Paul Abbate

Secret Service Director Ronald Rowe Jr., left, speaks with FBI Deputy Director Paul Abbate before testifying on the security failures leading to the assassination attempt on former President Trump on July 30, 2024. (Roberto Schmidt/AFP via Getty Images)

"So you're telling me the guy that took eight shots at the former president has apps and that we can't get into," Graham repeated. "Maybe if you could get into it, it would reveal some relevant information."

"That is correct, Senator," Abbate said.

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"So if he were talking to some foreign power and I don't think any foreign power would hire this guy, but if this was some great plot by the Iranians," Graham said. "How do we solve this problem?"

"Senator, you know, as we've been saying, we need a solution that provides lawful access," Abbate said.

US Senator Lindsey Graham

Sen. Lindsey Graham listens as Sen. Rand Paul speaks during a joint committee hearing on the security failures leading to the assassination attempt on former President Trump, at the US Capitol on July 30, 2024. (Roberto Schmidt/AFP via Getty Images)

The FBI previously said it had successfully gained access to Crooks' phone.

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"FBI technical specialists successfully gained access to Thomas Matthew Crooks’ phone, and they continue to analyze his electronic devices," the agency wrote in a press release. 

Ronald Rowe Jr.., Paul Abbate, audience members watch as a photo is getting displayed during hearing

Secret Service Director Ronald Rowe Jr. and FBI Deputy Director Paul Abbate testify as a photo is being displayed detailing the events that led to the July 13 assassination attempt of former President Trump. (Kevin Mohatt/Reuters)

FBI officials said on a Monday call with reporters, though, that encryption has been a challenge, including foreign-based encrypted email accounts. The FBI said there has been no indication of foreign involvement with Crooks' plot, but investigators have hit delays getting into those accounts.

The joint hearing with top officials from the U.S. Secret Service and FBI is the third congressional proceeding in just over a week focused on the shooting at Trump's rally, where the former president and two others were injured, and one attendee was killed.

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The fallout from the July 13 attack led to the resignation of former Secret Service Director Kimberly Cheatle, who announced her decision to step down after she faced blistering criticism following her testimony before the House Oversight and Accountability Committee.

Rowe, the agency's deputy director, was subsequently appointed as acting director of the Secret Service.