SAN BERNARDINO, Calif. -- FBI agents Saturday raided a Riverside home belonging to a friend of San Bernardino shooter Syed Rizwan Farook as they try to determine whether the man purchased two of the semiautomatic rifles used in the massacre, according to a law enforcement source.
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.
The search warrant was served at the home on Tomlinson Avenue, according FBI spokeswoman Laura Eimiller said. She did not have a specific address.
"The warrant has been sealed by the court and I am prohibited from commenting further," she said.
Victor Venegas, who lives in the neighborhood, said law enforcement showed up at a home in the 3800 block of Tomlinson Avenue early Saturday and stayed for 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.
Farook, his parents and siblings lived on Tomlinson for several years before moving out a few months ago. Marquez lived next door.
While Farook generally kept to himself, the one exception was his friendship with Marquez, who like him, loved to tinker with cars, neighbors said.
On Thursday, Gustavo Ramirez, who said he was Marquez's stepdad, told a Los Angeles Times reporter he and his wife hadn't heard from Marquez since Wednesday afternoon and were concerned. Ramirez said it was unlike Marquez not to come home.
On Friday someone had put up a sign in the family's yard that said: "Please keep off the property thank you."
The garage door appeared to have been busted and a window was shattered.
President Barack Obama vowed Saturday Investigators would "get to the bottom" of the massacre as new details emerged about the woman at the center of the terrorism investigation.
One of the two assailants, Tashfeen Malik, pledged allegiance to an Islamic State leader in a Facebook posting, officials said. The other shooter, her husband, Farook, had contact with people from at least two terrorist organizations overseas, including the Qaida-affiliated Nusra Front in Syria, a federal law enforcement official said.
On Saturday, several news organizations including CNN and the Associated Press reported the Islamic State extremist group had described the couple as "supporters" of the group in an online radio broadcast.
The broadcast declared "we pray to God to accept them as martyrs" but did not say whether ISIS played any role in the planning of the attack.
FBI Director James Comey said the assailants showed signs of "radicalization" but there was no evidence they were part of a larger terrorist network.
Obama, in his weekly radio address Saturday, said investigators were still trying to get a "fuller picture" of shooters' motives.
"It is entirely possible that these two attackers were radicalized to commit this act of terror," the president said. "And if so, it would underscore a threat we've been focused on for years -- the danger of people succumbing to violent extremist ideologies."
Farook and Malik died in a police shootout Wednesday, several hours after bursting into a holiday potluck for the San Bernardino County Health Department and killing 14 people.
Pakistani intelligence agents say they have questioned members of Malik's extended family in the province of Punjab, an area that is considered a stronghold of Islamist militant organizations.
Malik belonged to an educated, politically influential family from Karor Lal Esan in Layyah district. Malik Ahmad Ali Aulakh, a cousin of Malik's father, was once a provincial minister. Residents said the Aulakh family is known to have connections to militant Islam.
"The family has some extremist credentials," said Zahid Gishkori, 32, a resident of the Layyah district in the area who knows the family well.
Officials cautioned Malik's Facebook posting did not mean the militant group directed her and her husband to carry out the attack, and investigators think it instead suggests the couple had become self-radicalized.
The Malik family moved to Saudi Arabia when she was a child, but Tashfeen traveled frequently to the Punjab region to visit family and she returned there to attend Bahauddin Zakariya University in the city of Multan in southern Punjab to study pharmacology from 2007 to 2012.
After college she returned to Saudi Arabia, and from there moved to the U.S.
A family member in her hometown of Karor Lal Esan, who asked not to be identified, told the Los Angeles Times that Malik was "a modern girl" who became religious while studying at the university.