Syed Farook
Syed FarookReuters

FBI agents on Saturday raided a Riverside home belonging to a friend of San Bernardino shooter Syed Farook, The Los Angeles Times reported.

A law enforcement source told the newspaper the raid was connected to an investigation into whether the man purchased two of the semiautomatic rifles used in the massacre.

The source, who asked to remain anonymous because the case is ongoing, said officials have been trying to talk to the man to see what he knows about the attack. It's far from clear whether the man had anything to do with the violence or even knew what Farook did with the guns, the source added.

A second source said the guns were purchased three years ago.

Victor Venegas, who lives in the neighborhood, told The Los Angeles Times law enforcement showed up at a home in the 3800 block of Tomlinson Avenue early Saturday and stayed a few hours.

He and other neighbors have said Enrique Marquez, Jr., a young man who lived at the home, and Farook appeared to be good friends. The source said Marquez is the person the FBI is seeking to interview.

Earlier on Saturday, President Barack Obama admitted the California shooting was a terrorist attack and vowed investigators would "get to the bottom" of it.

On Friday, it was reported that Tashfeen Malik, Farook’s wife who carried out the shooting attack with him, pledged allegiance to the Islamic State (ISIS) leader in a Facebook posting.

It is believed Farook had contact with people from at least two terrorist organizations overseas, including the Al-Qaeda-affiliated Al-Nusra Front in Syria.