Comey said that in late 2013, before the FBI suspects Syed Rizwan Farook and Tashfeen Malik met in person, "they [were] communicating online, showing signs of their -- communicating their joint commitment to jihad and martyrdom."
"So far we have found no evidence of posting on social media by either of them at the time period and thereafter reflecting their commitment to jihad and martyrdom," he said. "These communications are private messages, not social media messages."
Comey previously testified that in the messages the FBI was able to recover in the days after the attack, the couple was talking to each other about extremism, but today marked the director's first reference to the messages being private.
A small number of public posts recovered by ABC News from Facebook account under a different name that authorities believed was used by Malik do not show particularly incendiary language, but one gives a vague warning to "coconut Muslims," a derogatory term sometimes applied to pro-Western Muslims.
Sen. Charles Schumer, D-N.Y., said Sunday, "Had they checked out Tashfeen Malik maybe those people in San Bernardino would be alive."
The DHS told ABC News that it was reviewing its policy and already had pilot programs exploring the potential use of social media in vetting.
Comey added the FBI does not scour the private emails of American citizens, like Farook, without probable cause that they’re somehow linked to terrorism. He said, “I think that’s the way we want it.”