San Bernardino shooting suspect Syed Rizwan Farook was 28 years old, born in Chicago to Pakistani parents. He was raised in Southern California and worked for the San Bernardino County Department of Health for five years.
The FBI won't call the shooting a terrorist act yet, but it is leading the investigation because the case has some hallmarks of terrorism. But officials stress they still don't know the motive.
Officials tell CBS News Farook and his wife Tashfeen Malik were not on any U.S. watch lists. But two law enforcement sources say they have found evidence Farook had contact with a person in the U.S. and other people overseas with suspected ties to terrorism.
Investigators are focusing on the extent of those contacts -- and whether Farook may have been influenced or possibly radicalized.
Farook, a U.S. citizen, graduated from California State San Bernardino in 2010. He turned to online dating websites in search of a wife.
He found Tashfeen Malik, who met and became engaged in 2013, when Farook made trip to Saudi Arabia during the annual Muslim pilgrimage known as the Hajj.
In 2014, Malik applied for visa at the U.S. embassy in Islamabad, Pakistan as his fiancee. Farook returned to Saudi Arabia that July to bring her to the U.S. Earlier this year, the couple had a baby girl.
But court documents reveal other parts of Farook's family life were turbulent.
In November 2014, Farook's father threatened suicide in front of Farook and his brother.
Last February, Farook's mother took out a restraining order against his father, saying he was bipolar and abusive.
All of this is now being looked at by the FBI, which seized computers, thumb drives and other electronic devices and shipped them to Washington for analysis.
Farook's wife passed counterterrorism screening as part of her visa application process. But until law enforcement determines the true motive in this attack -- be it terrorism or workplace violence -- it's not clear if warning signs were actually missed.
One of Farook's co-workers told CBS News correspondent David Begnaud he had a sense that Farook was becoming radicalized after getting married.
That worker narrowly missed the shooting. San Bernardino health inspector Christian Nwadike said he and four other men were in the bathroom when the first shots were fired.
"When the blast came in, I lost every feeling, I kept thinking this may be life or death," Nwadike told CBS News. He stayed on the floor of the bathroom for about 10 minutes, but could hear what was happening outside.
"There were cries, there were shots," he said.
Nwadike, who's originally from Nigeria, sat in a cubicle next to Farook for 5 years.
"When he came back from Saudi Arabia, he started growing beards -- that was the change," Nwadike said. He believes Malik helped radicalize Farook.
"Yes, by the wife, I think he married a terrorist," he said.
Nwadike said Farook was never violent or rude, and that "he rarely talked."
"I couldn't believe it, that's what I'm missing, there's no way that I can look at him and see attached to this," Nwadike said. "But it happened and it was him."