Chris Krebs, a former top Cybersecurity and Infrastructure Security Agency (CISA) official, is leaving the private sector to challenge a Trump administration probe.

Krebs said in a Wednesday email that he was “stepping away from” the cybersecurity company SentinelOne “effective immediately.”

“For those who know me, you know I don’t shy away from tough fights. But I also know this is one I need to take on fully – outside of SentinelOne. This will require my complete focus and energy. It’s a fight for democracy, for freedom of speech, and for the rule of law. I’m prepared to give it everything I’ve got,” the former CISA director added later.

Krebs, who was insistent that the U.S.’s elections were not compromised, pushed back in 2020 against allegations from now-President Trump that the election had been fraudulent.

In a memo from last week, Trump ordered a probe into “Krebs’ activities as a Government employee, including his leadership of CISA” by Attorney General Pam Bondi and Homeland Security Secretary Kristi Noem. 

The president said in his memo that the probe needed to find “any instances” in which the former CISA director’s behavior “appears to have been contrary to suitability standards for Federal employees” or in which he was “involved the unauthorized dissemination of classified information.”

“It’s about the government pulling its levers to punish dissent, to go after corporate interests and corporate relationships,” Krebs said in a Wednesday interview in The Wall Street Journal, the first to report on the news.

“It’s the same thing we’ve seen with the law firms, they’ve gone after clearances, they’ve gone after contracts. It’s a novel and expansive strategy they are taking on and it should concern everyone,” he added.

The Hill has reached out to the White House for comment.