The San Bernardino rampage was the deadliest US gun incident since the massacre at Sandy Hook Elementary School in Newtown, Connecticut, in December 2012, in which 27 people, including the gunman, were killed.
“I don’t think any community is immune,” said San Bernardino mayor Carey Davis.
“Certainly, we don’t anticipate that kind of thing happening here. It was a shock.”
Wednesday’s carnage amplified concerns about gun violence and security after deadly assaults at a Planned Parenthood clinic in Colorado Springs last week and the attacks in Paris three weeks ago by Islamic State militants that killed 130 people.
President Barack Obama called for gun law reform to reduce the likelihood of mass shootings.
San Berdo Mayor Carey Davis: "City is still on alert. We need to stay cautious but it is not a time to panic" pic.twitter.com/QYiHbUD87C— Conan Nolan (@conanNBCLA) December 3, 2015
“We have a no-fly list where people can’t get on planes but those same people who we don’t allow to fly could go into a store right now in the United States and buy a firearm and there’s nothing that we can do to stop them,” he said in an interview with CBS News.
In addition to the FBI and Bureau of Alcohol, Tobacco, Firearms, and Explosives, US attorney general Loretta Lynch said the US Marshals Service would assist state and local authorities to investigate the attack.
The attack in San Bernardino, a largely working-class city 100km east of Los Angeles, appeared to differ from other recent US killing sprees in several ways, including the involvement of two people rather than a lone perpetrator.
At a news conference called by the Los Angeles area Council on American–Islamic Relations (CAIR), the brother-in-law of Farook, Farhan Khan, said he was bewildered by the news.
“Why would he do that? Why would he do something like this? I have absolutely no idea. I am in shock myself,” said Khan.
Co-workers told the Los Angeles Times they were surprised to hear Farook’s name linked to the shootings since he was quiet and polite and did not appear to bear grudges.
Hussam Ayloush, executive director of CAIR in the Los Angeles area, appealed to the public not to jump to conclusions about the suspects’ motives.
“Is it work? Is it rage-related? Is it mental illness? Is it extreme ideology?” he said.
“We just don’t know.”