Here's how House Majority Leader Eric Cantor became aware of the David Petraeus matter, according to a senior aide to Cantor.

On Saturday, Oct. 27, Cantor spoke by phone to an FBI employee who told him about an investigation, including the details about Petraeus' affair , and said he was concerned that classified information had been compromised.

Read about the emails that launched the FBI investigation here.

Cantor then asked his chief of staff, Steve Stombres, to inform FBI Director Robert Mueller. Because the federal government was closed Monday and Tuesday of that week because to Hurricane Sandy, Stombres did not connect with Mueller's chief of staff until Wednesday, Oct. 31. Mueller took the information, but gave no indication whether there was an investigation, according to the aide.

The senior aide also said Cantor did not inform anyone else.

Indeed, House Speaker John Boehner did not find out about Cantor's role in this until the story (of Cantor's contact with the FBI) broke two days ago . Cantor believed the FBI agent was credible enough to pass on the information to Mueller, but, given that it was a single source whom he had never met, he did not believe there was a need to pass the information on to his fellow House leaders.

Cantor's office won't say to whom he spoke at the FBI, or even characterize what the person does at the Bureau.

As previously reported, the FBI employee first contacted Rep. Dave Reichert, R-Wash., who then put the employee in touch with Cantor.