Last Updated Feb 18, 2016 9:08 PM EST
CORONA, Calif. -- FBI agents on Thursday were searching the California townhome of the brother of one of the shooters in the San Bernardino terror attack. The brother is a Navy veteran who earned medals for fighting global terrorism.
Sources told CBS News the search was done in connection with the investigation into the attack, CBS News homeland security correspondent Jeff Pegues reported.
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.
Farook and his wife killed 14 people in the Dec. 2 terror attack at a meeting of his coworkers in San Bernardino, about an hour east of Los Angeles.
Syed Raheel Farook was in the Navy from 2003 to 2007, military records show. During his stint, he received the Global War on Terrorism Expeditionary Medal and the Global War on Terrorism Service Medal, among other awards.
After going through training in the family's native Illinois, Syed Raheel Farook served for three years aboard the aircraft carrier USS Enterprise as an information system technician.
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.
The search warrant came a day after Apple CEO Tim Cook said the company would fight federal government efforts to help the FBI hack into an iPhone that had been used by Syed Rizwan Farook.
A federal magistrate ordered Apple to help the FBI get into the phone but Cook said doing so would mean building a "backdoor" that would bypass digital locks protecting consumer information on iPhones. He says the software would be too dangerous to create.
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.