Attorney General William Barr said Thursday that the Russia investigation into President Trump and his associates was “one of the greatest travesties in American history,” and the culprits will be prosecuted if they broke the law. The years-long Russia probe divided the nation and hamstrung Trump’s presidency, but resulted in no charges against the president.

Last May, the attorney general assigned U.S. Attorney John Durham to review the intelligence gathering aimed at the Trump campaign in 2016 through to his Jan. 20, 2017, inauguration.

Last Fall, Durham—who has a reputation for being a “hard-charging, bulldog” prosecutor—reportedly expanded his probe to include “a post-election timeline,” adding agents and resources to the case.

In December, Barr told Fox News host Martha MacCallum that Durham was looking into “private actors” as well as former and current government employees who were involved in the Russia hoax.

During his appearance on Fox News’ “The Ingraham Angle” Thursday, Barr provided viewers with yet another update on the ongoing probe.

The AG stressed that Durhams’s primary objective wasn’t to just produce a report, but to prosecute those who violated the law.

“He is looking to bring to justice people who were engaged in abuses if he can show that they were criminal violations,” Barr told host Laura Ingraham.

“My own view is that the evidence shows that we’re not dealing with just the mistakes or sloppiness,” he added. “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.”

Barr said the president had “every right to be frustrated” by the investigation. Trump for years used Twitter as a sounding board to complain about the “witch hunt,” lashing out at his accusers and their fake news enablers.

“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.”

The attorney general also addressed the FBI’s abuse of the Foreign Intelligence Surveillance Act (FISA), saying he believed new “safeguards” would “enable us to go forward with this important tool.”

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.”

Former Trump Campaign advisor George Papadopoulos in October of 2016 denied that the Trump campaign was involved in the hacking of the Democratic National Committee, yet the FBI never relayed that potentially exculpatory information to the FISA Court despite it being recorded by an FBI confidential source.

The OIG recently reviewed 29 other applications for secret warrants, and found that the FBI violated the rules with an average of 20 errors per application. The widespread violations, which date back to at least 2014, have prompted some to suggest that the FBI was in the habit of using the surveillance tool to find dirt on political enemies.

“I think it’s very sad and the people who abused FISA have a lot to answer for,” Barr told Ingraham. “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.”