Let's hope not. Be vigilant!
I would bet that F-15s are being scrambled in SoCal. We should get them airborne on the east coast, too (in addition to those already flying CAP).
It could be a diversion. But if it is, it would be a suicide mission diversion. There would be no way for the shooter to survive, he'd die for the effort of creating the diversion.
I hope this isn't part of a larger plot to cause terror around the country.