FBI Deputy Director Andrew McCabe just so happened to be investigating Jeff Sessions for misleading Congress when Sessions fired him.

The air of corruption around the Trump administration’s firing of FBI Deputy Director Andrew McCabe just got a lot thicker with the bombshell revelation that McCabe was targeting the man who fired him.

Attorney General Jeff Sessions fired McCabe last week after months of pressure from Trump, who waged a relentless and very public smear campaign against the FBI leader.

According to ABC News, McCabe authorized a criminal investigation into Sessions almost a year ago after the attorney general told the first of several lies under oath to Congress.

Although one source claimed Sessions did not know about the investigation when he fired the deputy director, “an attorney representing Sessions declined to confirm that.”

That’s a significant unknown. Sessions was forced to recuse himself from the Russia probe because an investigation of the Trump campaign could have made him a tangential target. That he might have been the direct target of a perjury investigation would seem to constitute an even more severe conflict of interest.

Sessions’ attorney also told ABC News that the perjury investigation had been closed recently. But last week, it was reported that at least three witnesses have told investigators that Sessions lied under oath about a Trump campaign meeting with now-convicted Mueller informant George Papadopoulos.

The firing was already badly tainted by Trump’s improper calls for his dismissal. That firing occurred just days before McCabe was to retire with a full pension — exactly as Trump had demanded. Then Trump made it obvious that his intent was to discredit McCabe as a possible witness.

Now Trump’s attorney general has to answer for his role in a firing that is looking dirtier by the minute.