SAN BERNARDINO, CALIF. — Law enforcement agents on Sunday again searched the home of a man suspected of providing San Bernardino shooter Syed Rizwan Farook with the military-grade rifles he and his wife used to gun down 14 people, expanding the investigation into the deadliest terrorist attack on U.S. soil since Sept. 11, 2001.

A team of three officials spent about 30 minutes inside the home of Enrique Marquez, a former neighbor of Farook, and left carrying a large cardboard box. The box’s contents were unknown, and the officials declined to identify themselves or their agency to reporters outside.

The search at the modest suburban home, the second in two days, took place as new details surfaced about Marquez, who officials say bought the DPMS and Smith & Wesson AR15 rifles that Farook and his wife, Tashfeen Malik, used in the Dec. 2 rampage.

Marquez, who works as a Wal-Mart security guard, checked himself into a mental health facility on Friday; it is not yet clear if he has already been questioned by authorities or if he will be charged.

Four days after the attack on a gathering of county health workers, a picture is slowly emerging of the couple’s past and their apparent radicalization even as their lives followed a seemingly ordinary course: work, marriage, child. The couple’s daughter, born in May, is in the care of child protective services.

Friends and family described Farook, who was born in Illinois and grew up in California, as devout and conservative. Those who prayed with him at local mosques said the 28-year-old spoke about his personal life to few people.

On Sunday, Italian publication La Stampa published an interview with Farook’s father, also named Syed, in which he said his son had harbored anti-Semitic animosity. Reached at his son Raheel’s home on Sunday morning, the elder Farook said his views differed from those of his son.

“He was going towards (conservatism),” he told reporters through the gate of the home. “His views were conservative, my views were liberal.”

He also said that Syed Farook had quarreled with a Jewish coworker. One of the fellow county health inspectors killed in the attack was Nicholas Thalasinos, who converted to the Messianic Jewish movement of Christianity three years ago and who frequently posted online about Israel and politics.

Kuuleme Stephens, a friend of Thalasinos, said she had spoken with him by phone about two weeks before the attack, reaching him when he was having a conversation with Farook about the nature of Islam and Israel’s place in the Middle East.

But she downplayed the significance of the conversation. “It wasn’t an argument,” she said. “No one was raising their voices.”

Investigators are also working to determine what other attacks the couple may have planned. The rifles they used had been altered to make them more lethal, and a major arsenal was found in their two-story townhome, including 12 pipe bombs and thousands of rounds of ammunition.

During an appearance on Fox News on Sunday, Rep. Michael McCaul, R-Tex., chairman of the House Homeland Security Committee, said investigators are trying to determine where the couple got the money to buy their weaponry.

“There’s a serious investigation ongoing into what she was doing in Pakistan and in Saudi,” McCaul said. “We think that she had a lot to do with the radicalization process and perhaps with Mr. Farook’s radicalization from within the United States.”

“The wild card here is the wife, Malik,” he added.

One of the few known clues about Malik’s beliefs was a posting she made on Facebook around the time of the attack, pledging loyalty to Islamic State leader Abu Bakr al-Baghdadi.