Argument at Party May Have Sparked Shooting One suspect reportedly left after dispute and then returned, armed By John Johnson, Newser Staff Posted Dec 2, 2015 7:19 PM CST 162 comments Comments Police escort people from the building and surrounding buildings at the site of the mass shooting. (James Quigg/The Victor Valley Daily Press via AP) (Newser) – Authorities still haven't officially weighed in on a motive for Wednesday's shooting in San Bernardino that killed 14, but the Los Angeles Times reports that it may have been sparked by something mundane-sounding: an argument at a holiday office party. The newspaper quotes an anonymous federal official who says one of the gunmen is believed to have gotten into a dispute at the function for county employees. He then reportedly left the gathering and returned with one or two others, armed with long guns. “They had their appearances covered but a witness believed it had been someone who worked there,” one official, also anonymous, tells the New York Times.