California police were working yesterday to discover why a man and a woman opened fire at a party of his co-workers in the south of the state, killing 14 people and wounding 17 in an attack that appeared to have been planned. Syed Rizwan Farook, 28, and Tashfeen Malik, 27, who had a six-month-old daughter, were killed in a shootout with police after Wednesday's bloodshed at the Inland Regional Centre, in San Bernardino, a social services agency at which Farook worked as an inspector.San Bernardino police chief Jarrod Burguan said the motive was unknown. He and David Bowdich, an assistant regional FBI director, said it had not been determined if terrorism was a factor.The guns used in the attack were legally purchased in the US, the Associated Press reported.Farook was US-born: Malik's nationality is unknown.Farook's family and co-workers struggled to make sense of the shooting. His brother-in-law went on camera and said he had "absolutely no idea" why Farook would stage a massacre.Burguan said Farook was a county public health employee who attended the party, held at the centre, but at some point stormed out.He returned with Malik to open fire on the party.The couple were dressed in assault-style clothing and placed several bombs at the scene, which police detonated.Burguan said the way the couple were equipped indicated that there was "some degree of planning" behind the attack.Co-workers told the Los Angeles Times that they were surprised to hear Farook's name linked to the shootings because he had always been quiet and polite.They said he had travelled to Saudi Arabia and had returned with his new wife.Hussam Ayloush, executive director of the Council on American-Islamic Relations, appealed to the public not to jump to conclusions about the suspects' motives. "Is it work? Is it rage-related? Is it mental illness? Is it extreme ideology?" he said. "We just don't know."..