LAURA BARRON-LOPEZ: Let's turn now to possible security lapses in New Orleans.

For that, I spoke a short time ago with Juliette Kayyem, a former assistant secretary at the Department of Homeland Security and faculty chair of the Homeland Security Program at Harvard's Kennedy School.

Juliette, thank you so much for joining us today.

Given your expertise, how was a vehicle able to ram into a crowd?

And, from a physical security standpoint, could more have been done to prevent this?

JULIETTE KAYYEM, Former U.S. Department of Homeland Security Assistant Secretary: The evidence is starting to suggest yes.

So, in 2016, New Orleans changed its sort of safety and security positioning for Bourbon Street specifically.

That was after two major terrorist attacks in Europe, in Nice in France and Berlin in Germany, in which automobiles were used.

In that instance, or afterwards, New Orleans put up three different security measures.

It's the barricades, the bollards, which we will get to in a second, and then basically trucks.

But it's basically sanitation trucks, so that you would have this layered security.

What we're starting to learn and what's being disclosed is that that second, these sort of cement entities that would really essentially tear up a car if it was trying to ram through Bourbon Street, were not functioning, that they were being upgraded, presumably for the Super Bowl in a couple weeks, and, therefore, were not ready for this big event.

And that's what everyone is focused on right now is whether alternative measures, alternative security were used, and whether they were sufficient enough.

Look, any terrorist who really wants to kill could have just gone down the street and gotten another group of people.

But, obviously, you want to protect areas that are going to have the greatest risk and the greatest density of people.

LAURA BARRON-LOPEZ: Juliette, authorities have said that the suspect may not have acted alone.

Was this a city security failure or something larger?

JULIETTE KAYYEM: The larger question, at least in terms of what we're hearing from public officials, that this perpetrator did not act alone.

We have no clarity on who he may have acted with and, therefore, whether the city is safe tonight and, of course, tomorrow, when they are going to finally host a delayed Sugar Bowl tomorrow night.

It's that discrepancy between saying that the city should be open and people should move forward and the potential that there might be co-conspirators is something that they're going to have to answer to.

It's a legitimate question for reporters and the citizens to ask of public officials.

If they are wrong about their being co-conspirators, that's actually good news.

It shows a horrible incident, but one that can be managed by the city and it can move forward faster.

LAURA BARRON-LOPEZ: You said that there should have potentially been a backup option to those barriers on Bourbon Street that were not being used at the time of this attack.

What next steps are you looking for in this investigation?

JULIETTE KAYYEM: I think an honest accounting.

There was a press conference today that seemed just remarkably defensive.

I don't think that's a good posture for New Orleans, nor for the police department.

We need an honest accounting of, what were those alternative measures?

Were they focused on the wrong events, so to speak?

In other words, a Super Bowl is in a couple weeks, and so they were rushing for that, but forgetting they had a high-risk, high-profile event.

What we also have to figure out is why -- were there sanitation trucks and were they removed after midnight?

So, any buildup to a risky event is also going to have a drawdown.

And that drawdown may have happened at 2:00 a.m., 2:30 a.m. Did that create greater vulnerabilities for the people who are -- who were still partying on the street on New Year's Eve?

Those are the questions, operational questions, that have to be asked and answered honestly, not just for New Orleans, but every other city that is going to do this.

Paris, for example, has learned they essentially keep a sort of hardcore security posture in Paris, almost impossible to get vehicles in for New Year's Eve, until 6:00 or 7:00 the next morning.

These may be the lessons that we have to learn from this tragedy that happened today.

LAURA BARRON-LOPEZ: Juliette, you write in "The Atlantic" today that New Orleans needs to return to normal as quickly as possible.

But how safe is it to be in New Orleans right now and is it feasible and safe for the Sugar Bowl to continue tomorrow?

JULIETTE KAYYEM: So, I think the delay was appropriate.

I think it needs to guarantee that there's no ongoing threat.

So, what kind of changes can they make to security planning for the bowl that will assure safety and also assure the perception of safety?

You want people to have a good time.

And I think that's -- I don't think there's anything wrong with that.

You don't want terrorism to hold captive an entire city indefinitely.

They may never find these people.

You want to be able to move forward.

So those were the two major aspects, both in terms of what an accounting of, is it safe?

Who are these potential co-conspirators?

And, secondly, what changes are they going to make to the security posture to move forward?

I am not a fan of cities closing down for long periods of time.

We have learned in the past they create more tension, more fear, more isolation.

They generally aren't beneficial in terms of finding people.

But, most importantly, they give the terrorists a narrative that is greater than they should.

It makes them feel more powerful: Look, we can close down the Sugar Bowl and all of New Orleans in the first week of 2025.

And I think there's something important about giving a counternarrative.

LAURA BARRON-LOPEZ: Juliette Kayyem, thank you for your time.

JULIETTE KAYYEM: Thank you.