Rampage reportedly sparked after gunman had an argument at a holiday party at the Inland Regional Center who left the scene and came back heavily armed to kill at least 14. It is not known if he left of his own accord or was kicked out, but sources say he returned heavily armed.
It is also reported that the suspects were dressed in 'assault-style' clothing and carrying assault rifles and handguns. He said a third person was seeing running from the scene, who has now been detained. He added that it is not known if the person is connected to the shooting.