LOS ANGELES (CBSLA.com) —  As the country and the city of Chattanooga continue to reel from Thursday’s deadly attack outside two Marine facilities minutes apart, the question remains why.

Questions surround the alleged gunman, also killed during the attack that left four Marines dead.

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CBS2’s Peter Daut spoke to a local terrorism expert to find out what might have prompted the attack and if the suspect was conversing with other terrorists via the internet.

US officials say there’s no indication the suspect was under investigation by the FBI or on the radar of federal law enforcement agencies but Aaron Cohen, the terror expert, is confident ISIS inspired the violence.

“There’s no doubt in my mind there will be more attacks like this. This is the tip of the iceberg,” Cohen said.

Cohen owns IMS Security and spent several years in Israel’s counter-terrorist operations unit.

He says today’s attack in Tennessee appears to be Islamic terrorism.

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“This is ISIS. This is how they operate,” Cohen said.

ISIS has been calling for ‘lone wolf’ style attacks like the on the military and police during the month of Ramadan, which ends tomorrow.

Cohen says ISIS and other terrorist groups have been using social media to spread propaganda and recruit people to do harm.

“They’re trying to show how easy it is for them to flex their muscle, and the internet is now a tool to use as a weapon of war,” Cohen says.

Earlier this month, the Senate’s Intelligence Committee approved a bill that would require social media companies to alert federal authorities when they become aware of terrorist-related content on their sites.

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Daut said it’s unclear when the senate might vote on the bill.