Former counterterrorism official Joe Kent has been under FBI investigation for months on suspicion he leaked classified information, three sources familiar with the case tell Axios. Why it matters: Kent propelled himself into national headlines Tuesday when he resigned his post and blamed Israel for tricking President Trump into launching the Iran war even though it posed " no imminent threat " to the U.S. Driving the news: Immediately after his resignation, administration officials said he had been "a known leaker" and had been cut out of briefings with the president. Semafor reported that Kent, who led the National Counterterrorism Center, had been placed under investigation prior to his resignation, which Axios independently confirmed. One of the sources said Kent was suspected of leaking to Tucker Carlson and another conservative podcaster. That source said the FBI was also examining leaked intel related to Israel and Iran. The big picture: Few details have been released because the investigation revolves around classified information. "He left quite an online paper trail and he has been monitored for months," one source familiar with the investigation told Axios. "He's going to try to say this was in retaliation for his resignation," that source said, "but it's the other way around: He quit because he's under investigation and he knew it." Zoom in: On Wednesday, Kent gave a two-hour-long interview to Carlson, an ally and fellow critic of the war and of Israel. Carlson proactively defended Kent on his show and said he was paying the price for previously predicting that war with Iran would be a disaster. "Joe Kent was right. Therefore, Joe Kent must be destroyed," Carlson said. "And there is, of course, this ongoing effort to do that, to dismiss Joe Kent as a tool of the Islamists, or a leaker." Kent didn't return messages seeking comment. The intrigue: It's unclear why Kent was not immediately fired if he had been placed under investigation before Tuesday. Kent had run afoul of the FBI last year when he tried to access investigative records into the murder of conservative activist Charlie Kirk, the New York Times reported . Kent believed a "foreign agent" may have been involved in the assassination, he said Wednesday on Carlson's show, and he didn't understand why the FBI would not want additional investigative help to track down any other suspects. An official familiar with the dustup said the reason was simple: "It's not a conspiracy. Kent has nutty ideas. We got the killer. And what we didn't need was a guy spinning alternate ridiculous theories about foreign death squads that the defense would use so the killer could go free."