Tears stream down the face of Tram Le (L), holding a cooler belonging to San Bernardino shooting victim Tin Nguyen, and Krystal Le, during Nguyen's funeral at Good Shepherd Cemetery in Huntington Beach, California December 12, 2015. [Photo/Agencies]

He and Farook also planned to attack State Route 91 with pipe bombs during afternoon rush hour, and then to shoot at law enforcement and emergency crews as they arrived on the scene, according to the affidavit.

Prosecutors said the pair bought guns, ammunition and tactical gear, and Marquez told investigators he agreed to purchase the weapons because "his appearance was Caucasian, while Farook looked Middle-Eastern."

He bought a Smith and Wesson M&P-15 Sport rifle in November 2011 and a DPMS model A-15 rifle in February 2012, each costing about $750, according to the affidavit.

Marquez also purchased explosives, specifically smokeless powder, as part of the pair's plans "to create bombs and commit mass killings," the affidavit said.