Massacre gunman's cell phone photos prompt bomb sweep of schools

San Bernardino mass shooter Syed Rizwan Farook reportedly had photos of a local California high school in his cell phone.

School officials say the FBI was able recover photos of the exterior of Carter High School in Rialto.

Farook inspected schools as part of his job, but the school said it was unusual for him to keep photos of its exterior.

After last week's attack, police used bomb-sniffing dogs to search schools Farook had inspected as part of his job.

This is just one of several chilling details that have been disclosed about Farook and his wife, Tashfeen Malik, who together opened fire at a social services center, killing 14 and wounding 21 people.

FBI: San Bernardino shooters were radicalized for years

Speaking before lawmakers Wednesday, FBI Director James Comey confirmed the couple shared radical, extremist views long before they shared wedding vows - going back as far as two years.

"As early as the end of 2013, they were talking to each other about jihad and martyrdom before they became engaged," Comey said.

That would have been months before Farook brought his bride-to-be into the U.S. from Saudi Arabia in 2014, using a fiancé visa.

Officials believe Malik was radicalized before she came to America, having lawmakers now questioning how thoroughly she was vetted before being granted that visa.

Another "and whether her marriage to Farook could have been part of a terrorist plan all along.

In response to a question by Sen. Lindsey Graham about whether Malik's marriage to Farook may have been arranged by a terrorist organization, Comey said he "did not know the answer" yet, but did not rule out the possibility.

"It would be a very, very important thing to know." The FBI is also zeroing in on Farook's friend and neighbor, Enrique Marquez -- also related to Farook by marriage -- who investigators say purchased the rifles the couple used in their attack.

CBS News has learned that Marquez told investigators that he and Farook were planning an attack in 2012, but they didn't follow through. Still, Marquez has not been arrested, as the role he may have played in the San Bernardino attacks remains unclear.

As the FBI continues to comb through evidence, it says it has an estimated 900 active investigations involving ISIS sympathizers and other extremists nationwide.

Comey said his greatest fear following last week's terrorist attack is "what we don't know, what we can't see."

Survivors and family members of the San Bernardino victims returned to the scene of the shootings Wednesday to meet privately with investigators who answered their questions.

Thursday marks the first funeral for a victim of the massacre, 27-year-old Yvette Velasco who was one of the youngest killed in the attack.