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A 14-year veteran of the Internal Revenue Service went public for the first time Wednesday as the whistleblower claiming to have information about alleged mishandling and political interference in an ongoing criminal probe into Hunter Biden.

Gary Shapley, who was recently removed from the Justice Department investigation, spoke to CBS Evening News ahead of a scheduled meeting with the House Ways and Means Committee Friday.

“There were multiple steps that were slow-walked – were just completely not done – at the direction of the Department of Justice,” Shapley told CBS News chief investigative correspondent Jim Axelrod in an interview Tuesday. “When I took control of this particular investigation, I immediately saw deviations from the normal process. It was way outside the norm of what I’ve experienced in the past.”

“For a couple years, we’d been noticing these deviations in the investigative process. And I just couldn’t, you know, fathom that DOJ might be acting unethically on this,” he added.

Shapley told CBS News that he was concerned about how federal prosecutors handled “a high profile, controversial” investigation. Multiple sources previously confirmed to CNN the person at the center of that investigation is Hunter Biden.

In a letter to a federal watchdog agency this month, attorneys for Shapley said he first raised concerns about “irregularities” in how the Justice Department was handling the case in the summer of 2020 during the Trump administration. Shapley said he continued to air his concerns about the case in the following years under the Biden administration.

A spokesperson for the US Attorney’s Office in Delaware, which is overseeing the Hunter Biden criminal probe, declined to comment, as did a Justice Department spokesperson. The IRS did not immediately respond to a request for comment.

Shapley claimed he was not blowing the whistle for political reasons, telling CBS that he’s “not involved with any of that stuff,” adding: “It’s not what I want to do. I’m just simply not a political person. This is a job, and my oath of office is to treat everybody fairly that we investigate.”

A tense meeting in October 2022, Shapley told CBS, was his “red-line meeting,” saying that “it just got to that point where that switch was turned on, and I just couldn’t silence my conscience anymore.”

Federal prosecutors have spent years, spanning three attorneys general, investigating Hunter Biden and have weighed bringing charges against the president’s son for alleged tax crimes and a false statement, as CNN has previously reported. So far, no charges have been filed, and Hunter Biden has denied wrongdoing.

Shapley’s attorneys had hoped their client could sit for a joint interview with House and Senate committees, and recently expressed frustration that a bicameral interview did not pan out.

On Wednesday, a Senate Finance Committee aide said the whistleblower’s team backed out of meeting with the panel.

“Committee staff on both sides agreed with counsel to meet directly with the whistleblower next week, however the whistleblower has since backed out of that agreement and declined an attempt to reschedule,” said Ryan Carey, a spokesman for Senate Finance Chair Ron Wyden, an Oregon Democrat. “Should the whistleblower wish to meet with Senate Finance Committee, Chairman Wyden’s staff stand ready to arrange a meeting on terms that comply with laws protecting taxpayer data and ensure a fair and rigorous investigation.”

The whistleblower’s legal team never agreed to a date for an interview with the Senate Finance Committee, according to a person familiar with the discussions.

This account was disputed by Shapley’s legal team, which said Wyden’s staff was “playing partisan games by releasing inaccurate information.”

“As emails show, our client didn’t ‘back out’ of anything because there was never anything to back out of,” the legal team said in a statement. “Before we sent our May 22 letter, the Senate Finance Committee never committed to an interview date and refused to consider a joint interview. Nothing prevents Senate staff from joining Friday’s interview if Chairs Wyden and Smith simply agree to a joint interview, as our client has expressed a preference for all along. We hope to see them at the interview this Friday.”

This story has been updated with additional reporting and reaction.

CNN’s Evan Perez contributed to this report.