So what proof is there that the San Bernardino shooting was terrorism?

I know - not good to ask for proof here - we just accept govt stories without questioning. I am asking anyway.

From what I've seen - an unnamed facebook executive - speaking on condition of anonymity - claims that the female posted something under an alias on the day of the shooting - and the post was immediately removed?


Is this the proof we have?


So what proof is there that the San Bernardino shooting was terrorism?