What happened in San Bernardino strikes home with Americans precisely because it happened at work.
And while the U.S. has been plagued by deadly workplace shootings, the idea of a home-grown jihadi gunning down his co-workers in the name of Allah is especially terrifying, according to experts.
"We're faced with a day-to-day barrage of news with regard to ISIS beheadings and very cruel, severe attacks from third parties in the Mideast," said Anthony Roman, a top investigations and risk management analyst. "The images we see of this activity is keenly frightening and alien to us."
So when we hear reports that something like that may have happened here, "it causes a perception of greater fear over the coffee table," Roman said.
The FBI has not said conclusively that Syed Rizwan Farook and his wife were motivated by terrorism when they slaughtered 14 people and wounded 21 more Wednesday at the Inland Regional Center. They were later killed in a clash with pursuing police.
Roman is convinced Farook was planning a terrorist attack of some kind, but not convinced his intended target were his co-workers at a Christmas party.
"I believe it was a crime of passion but that he was radicalized and was going to launch an attack on some target at some point," Roman said.
Terrorists know that private businesses are vulnerable, he added.
"The government, law enforcement and the military are better prepared than ever for terrorist attacks," he said. "But industry across the globe is wholly unprepared for his evolution."
Forensic psychologist Joel Dvoskin said Americans had been bracing themselves for a terrorist workplace attack for many years.
"We have been kind of told that something like this is going to happen and something like this did happen," he said. "That raises peoples' sense of doom that there is going to be more of this. And we don't know that."
While we live in a world where the average American has a greater chance of dying in a car crash or from lung cancer than a terrorist attack, we perceive ISIS and al Qaeda attacking us in our homes or at our jobs to be an even bigger threat, Dvoskin added.
"The reason terrorism is effective is because it causes terror," Dvoskin said. "This scares people to death even if it is a low likely event."
"Work is the place most of us spend the majority of our waking time," clinical psychologist Ani Kalayjian added. "And there is a lot more fear of people from the Mideast since 9/11. So this combination is why what happened in California makes people even more fearful, even though we know this is not the first workplace shooting in America."
"Fear is based on ignorance," Kalayian said. "When my family fled here from Syria in the 1970s I remember being called a 'dirty immigrant' or 'terrorist.' And this was in Bergen County, which is supposed to be affluent and educated."