What We're Following This Afternoon

A deepening mystery: FBI Director James Comey says the San Bernardino attackers sent messages on Facebook, but they were private and couldn’t have been caught by intelligence. News reports after the attack said Tashfeen Malik, one of the shooters, pledged allegiance to Abu Bakr al-Baghdadi, the ISIS chief, on her Facebook page.

New terrorism-alert system: The Department of Homeland Security rolled out a new National Terrorism Advisory System. The newest component of the alert system is called “Bulletins,” which provides an intermediate level of warning regarding potential terrorism threats.

Solitary confinement in New York: The state has agreed to change the way it handles solitary confinement in its prison system. The change is the result of a lawsuit brought about by New York Civil Liberties Union.

Our headlines from the morning are here.