Former top defense aide Kash Patel, three other witnesses appear before January 6 select committee

A former top Trump administration defense aide was among four witnesses to appear Thursday before the House select committee investigating the January 6 attack on the U.S. Capitol.

Kash Patel, the chief of staff to Christopher Miller, who was the acting Defense secretary when the Capitol assault took place, met with the committee behind closed doors for around four and a half hours. CBS News was first to spot Patel and his team as they arrived on the Hill and were greeted by a committee staffer. Though Patel did not respond to reporters' questions, he later issued a statement saying he had answered the panel's inquiries to the best of his ability.

"I have always been willing and able to share with the Committee, and the American people, the truth about the events of January 6—including the Department of Defense's preparation for and response to unrest at the Capitol," the statement read, later adding:  "The DOD Inspector General, under the Biden Administration, found no wrongdoing in its report on Jan. 6, as I shared with the Committee."

Patel is considered a major figure in the House select committee investigation, which is examining how the federal government – including the Defense Department and the White House – prepared for and responded to the events of January 6. The former aide to Republican congressman Devin Nunes was among the first set of witnesses to be subpoenaed by the committee in September.

On Thursday, the panel also questioned Stop the Steal organizer Ali Alexander for up to eight hours. The rightwing activist sought to persuade the committee he had "nothing to do with the violence or lawbreaking that happened on January 6," according to prepared remarks obtained by CBS News.

He told reporters as he arrived at the committee's offices that he would provide "thousands of records" to the committee, including evidence that would "exonerate" him and former President Donald Trump.

The committee also met with conservative law professor John Eastman and former Cybersecurity and Infrastructure Security Agency Director Christopher Krebs, a source familiar confirmed to CBS News.

Politico first reported Eastman's appearance. The select committee subpoenaed him for records and testimony in November, and its interest in him stemmed from post-election memos Eastman is said to have written that proposed ways former Vice President Mike Pence could overturn the 2020 presidential results on January 6 and throw the election to Trump.

It's unclear how much information Eastman gave to the committee on Thursday. On podcasts earlier this month, Eastman slammed the panel and vowed to assert his Fifth Amendment right against self-incrimination. 

Meanwhile, Krebs is not among the 45 witnesses who have publicly received subpoenas from the committee. The former cybersecurity official was fired by the Trump administration last November after his agency issued a statement declaring the 2020 presidential election was secure. CNN first reported his appearance before the committee.