Investigators have said Marquez bought the two assault rifles three years ago that wound up being used in the shooting.

Officials say Marquez has told them he did it as a favor, so that Farook would not have to go through a background check or be on record as the purchaser.

Authorities say Marquez has told the FBI that he and Farook talked about conducting some kind of attack in 2010 but called it off after unrelated terrorism arrests in southern California.

On Wednesday, FBI Director James Comey said agents have found no connection between Farook and the people arrested back then.