Officials have not announced a definitive link between the shooters in this week's deadly attack on a California Christmas party and terrorism, but counterterrorism experts say they're not surprised that evidence is pointing in that direction.

Vesna Markovic, a terrorism and suicide-bombing expert from the University of New Haven, says that acts of terror happen on a daily basis all around the world.

She says that while citizens should not live in fear, terrorist groups like the Islamic State and its supporters often choose to attack so-called soft targets, which are places where people gather without a heavy security presence.

The group will continue to inspire lone-wolf terror attacks, she says.

Markovic says while acts of terrorism date back to the first century, the idea of radicalized individuals acting on their own is a threat the country is still working on handling.

"People have a higher probability of being assaulted by either a street crime or mass shooting than terrorism and people still seem to be more fearful of terrorism," Markovic says.

Investigative affairs expert Kenneth Gray says radicalism is the biggest challenge law enforcement is facing. He says the best way for the public to be a helpful resource is to be alert and remember the adage -- if you see something, say something.

"Even if they're just suspicious of something, even if they don't have hard information, that would be the tip that stops an event from occurring," Gray says.