The home of Enrique Marquez
The home of Enrique MarquezReuters

Enrique Marquez, the former neighbor of the San Bernardino shooters who is accused of buying the rifles used in the attack, pleaded not guilty on Wednesday, ABC7 reported.

Marquez faces multiple charges in a federal indictment accusing him of conspiring with one of the shooters and to provide material support to terrorists, the news station noted.

He appeared in federal court in Riverside wearing an all-white prison jumpsuit with his feet shackled and his hands cuffed. He answered several questions from the judge with "yes your honor" and answered "not guilty" when asked to enter his plea to the indictment.

Prosecutors stress there is no evidence at this point that Marquez knew about Syed Farook and his wife Tashfeen Malik's plans to open fire at the Inland Regional Center in December.

However, they did say Marquez provided them with their assault rifles and that his failure to warn authorities about his purchase of the guns had deadly consequences, according to ABC7.

Marquez and Farook grew up next door to each other in Riverside. Farook introduced Marquez to Islam as a teenager a decade ago and indoctrinated him in violent extremism, according to the FBI.

The attack in San Bernardino killed 14 people and wounded 22 others. Farook and Malik opened fire at a building where Farook's colleagues from the San Bernardino county health department were meeting, then fled and were later killed in a shootout with police.

According to prosecutors, Marquez bought two rifles for Farook in 2011 and 2012 and the two planned to launch bomb and shooting attacks at Riverside City College, where they attended classes, and a notoriously gridlocked section of highway without exits.

The two never carried out those plans.

Marquez faces two counts of firearms violations for being the so-called straw buyer who purchased the guns in his name, noted ABC7. He also faces one count of marriage fraud and one count of making a false statement on immigration paperwork for his marriage to a Russian woman whose sister is married to Farook's brother.

If convicted on all charges, Marquez faces up to 50 years in prison. A jury trial was scheduled for February 23.

The FBI has said that Farook and Malik were both radicalized "for quite some time" and had taken target practice at Los Angeles-area shooting ranges, and once "within days" of the massacre.

It is believed Farook had contact with people from at least two terrorist organizations overseas, and investigators have also said Malik had pledged allegiance to the Islamic State (ISIS) group in a Facebook posting.

The FBI on Tuesday appealed for the public's help in piecing together the whereabouts of the two shooters.

Investigators have largely determined the movements of Farook and Malik on the day of the massacre, but there are still 18 minutes unaccounted for.