Is explained here. Samuel Jackson was partly right. Had the San Bernardino shooters been white, it would have been different. First, they're religion or politics would have been the prime and/or only cause of the violence, even if we didn't know the facts. If it turned out that these had nothing to do with it, then there would be no real going back and correcting the matter.
Likewise, had this fellow been a white Christian, then we would have days, perhaps weeks, of stories reminding us of America's racist past, the violence and evils of the Christian heritage, the anti-Islamic bigotry and hapless hordes of Muslims being butchered and slaughtered every day in America, and on and on.
As it is, the suspect is not very white, and pretty Muslim. No narratives to advance there. Expect a couple up date stories in the days to come. That is it. It's all so different now because of who turned out to be the possible culprit. Maybe Mr. Jackson wasn't being so silly after all.