Barr said he has seen troubling signs from U.S. Attorney John Durham’s ongoing probe into the origins of the two-year probe, which resulted in no allegations of wrongdoing against the president.

“My own view is that the evidence shows that we’re not dealing with just the mistakes or sloppiness,” Barr told host Laura Ingraham. “There was something far more troubling here. We’re going to get to the bottom of it. And if people broke the law and we can establish that with the evidence, they will be prosecuted.”

Trump “has every right to be frustrated” by the investigation, Barr added.

“What happened to him was one of the greatest travesties in American history — without any basis,” Barr said. “They started this investigation of his campaign. And even more concerning, actually, is what happened after the campaign. A whole pattern of events while he was president … to sabotage the presidency … or at least have the effect of sabotaging the presidency.”

Barr appointed Durham to review the events leading up to the 2016 presidential election and the origins of the Russia probe, through Trump’s Jan. 20, 2017, inauguration.

During Thursday’s show Barr also addressed what he described as abuse of the Foreign Intelligence Surveillance Act (FISA), saying he believed “safeguards” would “enable us to go forward with this important tool.”

” I think it’s very sad and the people who abused FISA have a lot to answer for,” he said, “because this was an important tool to protect the American people.

“They abused it. They undercut public confidence in FISA but also the FBI is an institution and we have to rebuild that.”

Justice Department Inspector General Michael Horowitz last year said the FBI made repeated errors and misrepresentations before the FISA Court in an effort to obtain the warrants against former Trump campaign adviser Carter Page. The court later found those warrants “lacked probable cause.”