BOCA RATON, Fla. - We spoke with a Florida Atlantic University professor who's encountered radical Islam.
If anyone understands Isis, it's FAU professor Robert Rabil. He's been studying terrorist groups since the nineties and encountered radical Islam in Lebanon in the eighties.
"ISIS has made it clear that it's going to go ahead and carry out terror attacks throughout Europe, even here in the states," explained Rabil. "This what i worry about, the growth, the increase of radicalism within Europe."
After hearing about the Brussels attack that killed at least 30 people and wounded 230 more.
"I was shocked as to what happened," said Rabil. "I was extremely furious."
He says it's a reminder of how crucial it is for Homeland Security to work with European nations in the fight against terrorism.
"We are cooperating with Europe but we have to deepen that intelligence and security cooperation," explained Rabil.
Rabil points out the number of jihadi recruited from Europe has doubled since 2014 to about 5,000 fighters, which is a contrast to the estimated 100 to 150 fighters in Syria and Iraq from the United States.
But Rabil says the threat to both continents in this age of cell phones and SIM cards is escalating.
"What you are seeing now is more of a concerted effort, more people being involved in caliphate jihadism and especially in ISIS," said Rabil.