It needs to be understood that the FBI had Farook and his terrorist activities on their radar for some time. Police and FBI scanners confirm that even before the final sots were fired, they knew it was Syed Farook who was involved.
How did they know? The better question is since they did know - WHY did they just watch this happen?
How many other terrorists are operating in plain sight even now with the FBI, the NSA other agencies monitoring their every move - yet nothing is done?
To your point, has it ever been answered why CAIR had a press conference with the family of Farook before the names of the terrorist were released???