Senate Judiciary Committee Chairman Lindsey Graham, R-S.C., announced that former FBI director James Comey will be testifying before the committee at the end of September to discuss the early stages of the Russia investigation, known by the codename Crossfire Hurricane.

After a Justice Department Inspector General report revealed details of how the FBI's applications for warrants to monitor former Trump campaign adviser Carter Page contained errors and omissions, while relying on ex-British spy Christopher Steele's unverified dossier, Graham has been out to find out exactly who was responsible.

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"The day of reckoning is upon us when it comes to Crossfire Hurricane," Graham said. "Former FBI Director James Comey has agreed to appear before the Senate Judiciary Committee on September 30th, without a subpoena. I appreciate Mr. Comey coming before the committee. He will be respectfully treated, but asked hard questions. I look forward to this hearing. I think it will be important to the American people."

Graham has repeatedly pointed to how Steele's sub-source told the FBI that the information in the dossier was unreliable. The senator believes that someone other than those present for the sub-source's interview must have known about this before the dossier was used to get a warrant for Page under the Foreign Intelligence Surveillance Act (FISA).

FBI Director James Comey is sworn in on Capitol Hill in Washington, Thursday, July 7, 2016, prior to testifying before the House House Oversight and Government Reform Committee hearing to explain his agency's recommendation to not prosecute  Democratic presidential candidate Hillary Clinton over her private email setup. (AP Photo/J. Scott Applewhite)

FBI Director James Comey is sworn in on Capitol Hill in Washington, Thursday, July 7, 2016. (AP Photo/J. Scott Applewhite) (The Associated Press)

“We’re not going to let the system blame some low-level intel analyst or case agent for defrauding the court,” Graham told Fox News' Maria Bartiromo in June. “I believe it goes to the very top, and I’m going to get to the bottom of it and that means Sally Yates and [Rod] Rosenstein, and [Andrew] McCabe and Comey are all going to come before the committee and they’re going to be asked, ‘What did you know and when did you know it?’”

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Now Graham will have the opportunity to ask Comey directly. He is still waiting on others.

"We are negotiating with Mr. [Andrew] McCabe, and we’re hoping to get him without a subpoena," Graham said. "Time will tell.”

Graham also said an invitation to testify has been sent to former FBI agent Peter Stzrok, who was involved in the Russia probe and drew notoriety for politically charged, anti-Trump text messages he sent to FBI attorney Lisa Page.

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Graham said that his committee sent a request to former special counsel Robert Mueller as well, in light of Justice Department records that revealed that the phones of multiple people on Mueller's team were wiped.

"Mr. Mueller has declined the committee’s invitation to appear to explain his report," Graham said. "He says he doesn’t have enough time to prepare. But I’m going to ask the Department of Justice and Inspector General Horowitz to look at this report that members of Mr. Mueller’s team erased information from their devices."