CORONA, Calif. » The investigation into the San Bernardino terror attack that killed 14 people burst back into public view today, when FBI agents searched the home of the brother of gunman Syed Rizwan Farook.

The FBI conducted an hours-long search of Syed Raheel Farook’s home in Corona, Calif. Curious neighbors and media outlets captured images of at least a dozen investigators carting out armloads of thick manila envelopes, a computer tower and an unidentifiable object so heavy it took two men to carry.

The search warrant is sealed, and FBI spokeswoman Laura Eimiller would not disclose any information other than to confirm a search was conducted at a Corona home in an ongoing investigation.

The massive investigation into the shootings has largely been progressing behind the scenes, with agents conducting hundreds of interviews and analyzing mounds of evidence.

Following the search of his home, Raheel Farook was not arrested and has not been named a suspect.

Messages left for attorneys representing the Farook family were not immediately returned.

Raheel Farook is a military veteran who earned medals for fighting global terrorism.

One of his neighbors, Stacy Mozer, described Raheel Farook and his wife, Tatiana, as ideal neighbors. The couple drove another neighbor to doctor’s appointments last year when she had cancer surgery, treated her to meals out and fetched her prescriptions for her, even paying for them, he said.

The couple frequently strolled with their 1-year-old daughter around the community of townhomes and took her to the pool.

“I would find it very hard to believe that they would be involved in any way,” he said. “I do know that if you have a family member, you don’t have control of their lives, and I don’t think they had control of their brother’s life.”

Mozer said the family’s home was searched twice after the December shooting, and authorities broke down the door on an earlier occasion.

To serve a search warrant, authorities must have probable cause that a crime was committed and items connected to the crime are likely to be found at the location.

Syed Rizwan Farook and his wife, Tashfeen Malik, opened fire Dec. 2 at a meeting of his San Bernardino County co-workers. They died hours later in a shootout with police. The 14 people killed marked the deadliest terror attack on U.S. soil since Sept. 11, 2001.

Farook’s family has said it had no inkling about the plot.

Raheel Farook was a Navy information system technician from 2003 to 2007, military records show. He was stationed aboard the aircraft carrier USS Enterprise and received the Global War on Terrorism Expeditionary Medal and the Global War on Terrorism Service Medal, among other awards.

The chief of the FBI’s Los Angeles field office told The Associated Press last month that some of the most basic questions related to the shootings had not been answered, including whether anyone else was involved. At the time, David Bowdich said investigators were not looking past anyone and had “a very open mind on this investigation.”

The search of the Farook home came a day after Apple CEO Tim Cook said the company would fight federal government efforts to help the FBI hack into an iPhone used by the gunman.

So far, the only person charged in connection with the attack is Enrique Marquez, a friend and former neighbor of Rizwan Farook’s. Marquez is charged with providing the assault rifles used in the massacre, making false statements about when he bought the weapons and conspiring with Rizwan Farook on a pair of previously planned attacks that were never carried out.

Marquez also faces charges of marriage fraud and lying on immigration paperwork. The FBI said he acknowledged that he was paid $200 a month to marry the sister of Raheel Farook’s wife, and he lied on immigration papers that he lived with her so she could stay in the U.S.

Marquez and his wife listed their address at the same Corona home that was searched by the FBI on Thursday.

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Myers reported from Los Angeles. Associated Press writer Amy Taxin in Tustin contributed to this report.