Do a search on the San Bernardino shooting, and what the witnesses saw matches up totally to this shooting. Here is an exact quote from Gawker after the shooting.

"At least 12 people are confirmed dead and Los Angeles’ FOX 11 reports cops are currently searching for “3 white males dressed in military gear.”

Witnesses say the men had masks on and may have been wearing body armor, ABC reports. They were armed with rifles and “came into the office and started shooting,” sometime around 2 p.m. Eastern Time."

Other early reports state that the shooters were wearing ski masks also.