According to a source familiar with the investigation that led to McCabe’s firing, Comey—then FBI director—asked the bureau’s internal Inspection Division to look into an Oct. 30, 2016, Wall Street Journal story that included leaks from inside the bureau. The Inspection Division took on the case and started trying to determine who was responsible for the leak. When they realized McCabe, the bureau’s deputy director, was a likely culprit, they handed off the investigation to the Justice Department’s inspector general, according to an IG report released late last week.

Attorney General Jeff Sessions cited that detailed IG report when he announced McCabe had been fired barely before he was eligible for his retirement.