NBC News has learned that early Saturday the FBI searched the Riverside, California home of the man authorities believe originally bought the assault rifles used in the San Bernardino shooting rampage that killed 14.
During the search, neighbors say, agents cut open the garage door with blow torches, used bomb-sniffing dogs, and temporarily detained the man's father and younger brother. The man's father told NBC News Saturday afternoon that he does not know where his son is and declined further comment.
Federal officials say the two assault weapons were originally bought in 2011 and 2012 by the man, said to be a friend of Farook's, but investigators don't yet know whether Farook gave him the money upfront, or bought the guns from him later.
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A neighbor who witnessed the search told NBC News that the man and Farook had been close friends since childhood but appeared to have grown more distant in recent months.
An FBI official said Saturday that the man is not considered a suspect in the shooting, and NBC News is not releasing his name.