The deadly attack on New Year's Day in New Orleans was shocking.

Fourteen people were killed, with dozens injured, after a man rammed a pickup truck into a crowd

of revelers.

In the aftermath, one chilling detail emerged.

There was an Islamic state flag in the truck.

And because it was New Year's Day, like the details were a bit slow to come in, but we kept seeing little things that made us think, oh, wow, could this be ISIS?

Could this be another attack just like the ones we've seen before?

And the more we learned, the more concerned we got.

And then, of course, the kicker was, whoops, they found an ISIS flag in this guy's truck.

And our thinking was, oh boy, here we go again.

Joby Warwick covers terrorism at the post. He wrote a book about ISIS.

He says the New Orleans attack shares ingredients with other recent attacks inspired by the group. What we've seen in the last few years is that more and more, these

attacks are not necessarily directed, coordinated in some way by the Islamic State, but people

are inspired by ISIS.

And then what you see are these seemingly random attacks around the world

in which somebody just gets the idea in their head

that they're going to be a terrorist

and they're going to become part of ISIS.

And the amazing thing about ISIS,

it's the easiest club in the world to join.

You don't have to be recruited or indoctrinated.

You just do something.

...