Hillary Clinton's response, however, was far more tempered than that of Donald Trump.
The Republican candidate called for North Atlantic Treaty Organisation to act saying it "should be used for a purpose" to wipe out the "cancer" of the terror group, as unconfirmed reports claimed the terror group has claimed responsibility for the attack.
'But I think it's also clear that as a result of these advances against ISIS and their main headquarters in Raqqa, their urgent desire to inflict terrorists attacks elsewhere has led them to accelerate, reaching out, not only directly, but indirectly through the radicalization online'. "Do you agree with that?"
"I would. I would", Trump told O'Reilly. "And I've been saying it for a long time".
"In Europe, one of their problems have been - and they better address this because it affects us, too - they don't share enough information even across their borders. It's bedlam. We have to get awfully tough and we have to get smart or we're not going to have a society, we're not going to have a world anymore".
Trump expressed his first thoughts on the attack via Twitter: "When will we learn?"
Both Hillary Clinton and Donald Trump condemned the apparent terrorist attack in Ffrance that left more than 80 people dead and dozens more critically injured.
United States leaders were quick to condemn the attack in Nice, where a man ran a lorry more than a mile through a crowded promenade during a Bastille Day celebration.
In a statement following the Instanbul attack, he said that the "whole world is stunned and horrified".
The Washington Post looks at how Trump "uses insults, threats and lawsuits to quiet critics". "We are with you in every way!"
Obama sent Congress a formal request last February, but lawmakers can't agree on what kinds of war they should authorize - and have often found it politically convenient to complain about the lack of a formal authorization without taking action to pass one. Of course, millions of others want their national military brand to bomb and kill more in what is obviously a vain effort to kill all of their enemies.
Mr Trump said North Atlantic Treaty Organisation should also be involved in the war. Folks, there's something going on that's really, really bad. "We are supporting North Atlantic Treaty Organisation and we should at least get something out of it and getting rid of ISIS and getting rid of this cancer that we're watching all over the world, that certainly would be a good thing".
The attack was the worst mass shooting in USA history, which killed 49 people and wounded 53 others.