Investigators believe that over several years, one of the alleged San Bernardino shooters, Syed Farook, had been in some sort of contact with several people who were on the FBI’s radar due to potential terrorism concerns, according to multiple sources.
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However, the sources stressed that the people Farook was in contact with were "not significant FBI targets" and "not subjects of significance," the sources said.
The nature of his contact with these individuals remains unclear.
The sources emphasized that Farook's contact with people under FBI review does not mean that he subscribed to terrorist ideology.
Investigators have still not determined if the shooting, which left 14 people dead and 21 others injured, was an act of terrorism. Investigators are also looking at whether the violence was workplace-related.
Farook worked for San Bernardino County and had been attending a work function and holiday event at the site of the shooting, the Inland Regional Center. He left the event at some point and appeared angry. Later he and the other suspect, his wife, Tashfeen Malik, returned and opened fire, killing 14.
One of the reasons why investigators suspect terrorism may be at play is that the bombs used appear to be similar to those laid out in al-Qaeda's Inspire magazine. That was a factor in the Boston marathon bombing, where two brothers were not directly tasked with the terrorist act but self-radicalized online.
More details about Farook and Malik have come to light today after police identified them as the two suspects in the shooting. Both were killed by police in a shoot out Wednesday afternoon.
Farook's most recent international trip came in July 2014 when he flew from Chicago to Jeddah, Saudi Arabia with a layover in London's Heathrow airport. He then flew back to the U.S. 11 days later and so did Malik, who entered the country on a fiancee visa. According to court records, the couple married three weeks later and a source tells ABC she didn't receive her green card until this summer.
Editor’s note: An earlier version of this story stated that Malik received her green card in 2014. She actually received it this past summer.