RIVERSIDE, Calif. (CBSNewYork/AP) — The FBI has not said what it was looking for in a raid early Saturday at the home next door to where San Bernardino shooter Syed Farook’s family used to live in Riverside, California.

Neighbors say authorities with guns drawn broke windows and used a cutting torch to get into the garage. A neighbor says an old friend of Farook’s is the person that lives in the house.

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A law enforcement official says that more than three years ago, that person bought two assault rifles later used in the shooting, but authorities haven’t been able to talk to him because he checked himself into a mental hospital after the attack. The official was not allowed to discuss the investigation publicly and spoke on condition of anonymity.

The FBI has said the man is not a suspect in shootings, though they want to question him.

Meanwhile, questions are being raised about Tashfeen Malik, who carried out the massacre with her husband, and how she came to the U.S. last year on a special visa for fiances of U.S. citizens.

Authorities said Friday that Pakistani citizen Malik, 29, pledged allegiance to the Islamic State group and its leader under an alias account on Facebook just moments before she and her husband, Syed Farook, opened fire on a holiday banquet for his co-workers, killing 14. They later died in a gunbattle with police Wednesday.

Malik, who had been living in Pakistan and visiting family in Saudi Arabia, had passed several government background checks and entered the U.S. in July 2014 on a K-1 visa, which allowed her to travel to the U.S. and get married within 90 days of arrival.

Malik was subjected to a vetting process the U.S. government describes as vigorous — including in-person interviews, fingerprints, checks against U.S. terrorists watch lists and reviews of her family members, travel history and places where she lived and worked.

The process began when she applied for a visa to move to the United States and marry Farook, a 28-year-old Pakistani-American restaurant health inspector for the county who was raised in Southern California.

Foreigners applying from countries recognized as home to Islamic extremists, such as Pakistan, undergo additional scrutiny before the State Department and Homeland Security Department approve permission for a K-1 visa.

It was not immediately clear what information Malik provided as a part of the background check by the State Department and U.S. Citizenship and Immigration Services or when she became radicalized.

“This is not a visa that someone would use because it is easy to get into the US, because there are more background checks on this type of visa than just about anything else,” said Palma Yanni, a Washington-based attorney who has processed dozens of K-1 visas. “But fingerprints and biometrics and names aren’t going to tell you what is in somebody’s head unless they somewhere have taken some action.”

The government’s apparent failure to detect Malik’s alleged sympathies before the shootings will likely have implications on the debate over the Obama administration’s plans to accept Syrian refugees. Attorneys representing Farook’s family deny that he or his wife had extremist views.

On Friday, ABC News reported that the address in her Pakistani hometown that Malik listed on her visa application does not exist. In response to a question about the ABC report, State Department spokesman Mark Toner said: “We are actively reviewing all of the information provided in the visa application and sharing it with our interagency partners as it relates to the investigation.”

The vetting process for refugees is similar, though not identical, to the one for fiance-visa applicants.

“Uncle Sam just looks on as an approving cupid and doesn’t pay as much attention as he should to the issuance of these visas,” said David North, a senior fellow with the Center for Immigration Studies, which advocates for stricter immigration policies.

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Refugees also submit to in-person interviews overseas, where they provide biographical details about themselves, including their families, friendships, social or political activities, employment, phone numbers and email accounts. They provide biometric information, including fingerprints. Syrians are subject to additional classified controls.

Republican lawmakers and governors across the U.S., as well as advocates for stricter immigration enforcement, have challenged the effectiveness of the vetting process for refugees.

New Jersey Gov. Chris Christie has said he wants assurances from the FBI that terrorists are not masquerading as refugees. He said the federal government hasn’t been sharing information about its vetting process.

“The single most important responsibility of the president of the United States, in my opinion, is to protect the safety and the security of the American people,” Christie said Tuesday.

Refugees must apply to become a legal permanent resident after a year. But almost as soon as they arrive, they are eligible to work and apply for some benefits.

Those who come to the U.S. on a fiance visa must marry a U.S. citizen within 90 days or leave the country. Following the marriage, the immigrant becomes a conditional resident for two years and must ask the U.S. government to remove those conditions at the end of that waiting period and undergo another background check. If the request is approved, the immigrant receives a green card. Immigrants can apply to become U.S. citizens five years after winning a green card.

“Can we improve the system as technology grows? There is always room for improvement, but to indict the entire fiance visa system because of this is not the right path,” said David Leopold, a past president of the American Immigration Lawyers Association.

Even those who intersected with Malik in California could not offer much insight, as she was rarely seen in the Muslim community.

The couple was married Aug. 16, 2014, and held their wedding reception at the Islamic Center of Riverside, said Dr. Mustafa Kuko, the center’s director. Kuko said he never met Malik because the party was divided into separate spaces for women and men.

“She never came to our mosque except once when they had their reception, and that night there were so many people around, my wife doesn’t recall exactly how she looks or who she is,” Kuko said. “We never saw her again.”

The mosque in Redlands, where the couple lived, had no record of Malik attending services or enrolling in programs for Muslim women.

“We really don’t know anything about that sister,” Khaled Zaidan, chairman of the board of directors of the Islamic Community Center of Redlands, said. “It really is a mystery what happened on Wednesday, how a woman could drop off a 6-month-old and commit a horrific crime killing all those innocent people.”

Among the 21 injured in the attack were two police officers hurt during the manhunt, authorities said.

The dead ranged in age from 26 to 60. Nearly all were county employees and some had ties to the Tri-State area.

The victims have been identified as Shannon Johnson, 45, Los Angeles; Nicholas Thalasinos, 52, Colton; Isaac Amanios, 60, Fontana; Bennetta Betbadal, 46, Rialto; Aurora Godoy, 26, San Jacinto; Larry Kaufman, 42, Rialto; Harry Bowman, 46, Upland; Yvette Velasco, 27, Fontana; Sierra Clayborn, 27, Moreno Valley; Robert Adams, 40, Yucaipa; Tin Nguyen, 31, Santa Ana; Juan Espinoza, 50, Highland; Damian Meins, 58, Riverside; and Michael Wetzel, 37, Lake Arrowhead.

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