West Virginia's Governor Patrick Morrisey said 24-year-old Staff Sergeant Andrew Wolfe, who was also shot in the attack, remains in critical condition.

For more on the president's call for immigration reforms, I'm joined by David Bier.

He's the director of immigration studies at the Libertarian Cato Institute.

Thank you for joining us today, David.

DAVID BIER, Director of Immigration Studies, Cato Institute: Thanks for having me.

LIZ LANDERS: OK, let's start with some of these social media posts from the president.

He wrote last night in a pair of posts demeaning immigrants and calling the country's immigration policies stupid.

What's your reaction to that?

DAVID BIER: Well, first of all, this was a horrific attack.

No one condones it.

This is an individual who should be prosecuted to the fullest extent of the law.

Unfortunately, what the president has taken away from this attack is that all of 53 million, as he says, immigrants to the United States, legal or illegal, are now seen as suspicious, as people who should be driven out of the United States, even denaturalized.

If you look at the rhetoric in that post, he can't find a single good thing to say about any of the immigrants from any country in the world.

And that's really what's different.

What I see here is, the president has for a long time talked about the problems with certain types of immigration, with illegal immigration, with refugees and others.

But this was really the broadest attack that I can remember on the immigrant population overall, both legal and illegal, even the naturalized citizens who have taken the oath to the Constitution of the United States.

LIZ LANDERS: Trump's post had a series of pledged reforms, including, but not limited to a permanent pause on migration from all Third World countries.

We heard that a few moments ago.

Remove anyone who is not a net asset to the United States.

End all federal benefits and subsidies to noncitizens and denaturalize migrants who undermine domestic tranquility.

How much of that can he follow through on?

DAVID BIER: Well, certainly, he's already trying to carry out the largest mass deportation campaign in the history of the United States.

He wants to deport millions and millions of people who are here illegally.

So now he's just adding to that campaign promise with trying to deport people who are in the country legally.

Now, taking away someone who has illegal permanent residence, their status, is quite difficult.

You have to prove your case against them.

You have to bring that before an immigration judge and layout exactly what immigration law they violated.

And what he's talking about here, net asset, all this stuff, there is some ambiguity in the law, but there's not that much ambiguity, and it will be difficult for him to actually follow through on that promise and effectively deport most of the legal immigrants in the United States.

LIZ LANDERS: The treasury secretary, Scott Bessent, is saying that his agency is going to issue proposed regulations clarifying that the refunded portions of certain individual income tax benefits are no longer available to illegal and other non-qualified aliens.

What benefits do those without legal status receive?

And do we know whether what Bessent posted about will have any substantial impact?

DAVID BIER: Usually, these benefits are based on the Social Security numbers that are available to them.

So, you submit your application for benefits along with your income tax return, checking that box that you have a Social Security number that is work-eligible, which is the basis for the refund or otherwise.

So I certainly support this type of proposal in terms of policy.

Unfortunately, Congress is the one who sets the rules for this, and they just went through this tax reform bill that they put forward and they didn't go all the way with this idea effectively barring most noncitizens from those.

And so really what he's advocating for is Congress to change the law.

We will see if that happens.

LIZ LANDERS: What trends have we seen in immigration recently?

And what impact could these changes that we're seeing from the president being proposed, what could those have -- impact on these immigration trends we're seeing?

DAVID BIER: Well, ultimately, the president's proposals from day one have been to restrict legal immigration.

He's come out with a number of different ideas on those lines, including the total shutdown of the refugee program, a ban on most immigration from 19 different countries, restrictions on the H-1B high-skilled visa.

So, across all the different categories of immigration that we have, he's looking to restrict.

This is the first time he's said an outright ban.

And when you think about who gets most legal immigrant visas to come to the United States, it is spouses of U.S.

citizens.

That's going to be the number one category that's targeted by a broad-based absolute ban on legal immigration to the United States.

And that's really cutting at the heart of family values and a lot of the other things that conservatives like to talk about.

LIZ LANDERS: David Bier from the Cato Institute, thank you so much for joining us this evening this holiday weekend.

We appreciate it.

DAVID BIER: Thank you.

Of course.