ROBERT SIEGEL, HOST:

We're going to be hearing a lot this week about the gang Frank Fuentes was alleged to have been involved with - Mara Salvatrucha, or MS-13. It was started by Central American immigrants in California prisons, and it has spread across the country and into Mexico and across Central America. President Trump is expected to go to Long Island this week, where the gang has been implicated in many violent crimes. Trump has made deporting MS-13 members a priority.

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PRESIDENT DONALD TRUMP: MS-13 is going to be gone from our streets very soon - believe me.

SIEGEL: That was back in May. So six months into the Trump administration, how has immigration enforcement affected MS-13? We're going to ask the police chief of the fourth-largest city in the country - Houston. Chief Art Acevedo, welcome to the program.

ART ACEVEDO: Hey, thank you. It's great to be on.

SIEGEL: And how much of the violent crime in your city, in Houston, is committed by gang members? And how much by members of MS-13 in particular?

ACEVEDO: Well, I think if you take a look at our violent crime, the vast majority of it is being committed by documented gang members. You know, we have about 20,000 documented gang members here in this city, and quite frankly, they're vicious. But MS-13 I would consider the worst of the worst. I consider them a transnational terrorist organization because of the nature and the viciousness of their activities.

SIEGEL: And when you speak of members of MS-13, do you assume that they're in the country illegally?

ACEVEDO: I would say that a good number of them are here as undocumented immigrants. Initially they were from El Salvador, but now they've spread their cancer throughout Central and South America and throughout the United States. They started in Los Angeles back when I was a young police officer with the California Highway Patrol. And a lot of them are. But some of them now are, you know, second-generation American-born citizens. And so we just have to go after them regardless of their documentation and go after them hard because they are vicious.

SIEGEL: By the way, when you speak of their viciousness and their - that when you speak of them as a cancer, what kind of offenses are you talking about? What leads you to say that?

ACEVEDO: Well, they are brutal. They're ruthless. They will kill without blinking an eye. We had a young lady that was brutally raped and murdered. And just the lack of empathy, the lack of respect, the lack of human decency with these guys that makes them - they celebrate homicide. They celebrate brutality. And they wear it as a badge of honor. And that's something that makes them extremely dangerous.

SIEGEL: Has there been any notable difference in deportations of MS-13 members, say, this year than in the first half of last year?

ACEVEDO: Not yet, but we do work closely with our HSI, Homeland Security Investigations, which is part of ICE. And what we've done here in Houston because of the violence being perpetrated by MS-13 and other gang members is that we've upped the ante. We've upped our resources. And quite frankly, we've - our federal partners, at our request, not just in Houston but around the country, have added additional resources, including the FBI and Homeland Security, to really focus nationwide on going the worst on the worst. And the worst of the worst really truly is MS-13.

SIEGEL: Has the talk of a crackdown in any way affected the willingness of people in Houston, let's say particularly in Latino communities, to report crimes or come forward as witnesses to crimes because of the fear that somebody might be deported?

ACEVEDO: For us and for other cities, we're seeing that it is having a chilling effect. You know, when we compared the first three months of 2017 versus the first three months of 2016 - and I'm almost done with the analysis for the second quarter of this year and the first of last year - we saw a almost 43-percent reduction in the reporting of sexual assaults by the Hispanic community, and we saw a reduction of the reporting of all violent crime by the Hispanic community.

Yet when we compared that to the rest of our communities and the other communities residing within the most diverse city in the country, which is Houston, Texas, we've seen an increase. And when you see that chilling effect, when the victims and witnesses of crime are hesitant to come forward because of the ugliness of this political debate, that is an absolute loss for all of us. And we should all be concerned.

SIEGEL: I mean, you're describing a perverse effect because you're getting numbers that could be construed as a reduction in crime or a reduction of crimes being reported. That's not what it is, is what you're saying.

ACEVEDO: No. The truth of the matter is when you talk to cops, they're telling me story after story of crimes being committed, of being able to identify the victim, but then having victims not want to cooperate, not want to come forward, and having to work two, three, 10 times as hard to get other community members to try to convince people to cooperate.

SIEGEL: We just heard a story about a Guatemalan young man who was deported after a criminal conviction. He had lived and grown up nearly his whole life in northern Virginia. He was found dead in that trailer in San Antonio, having re-entered the country. When gang members in your city, in Houston, are deported, do they typically come back across the border?

ACEVEDO: You know, my dad used to say that bad bugs don't die. They multiply. And I think in terms of MS-13, hopefully we put them in prison here for a long time when we catch them for these crimes because if we deport them, quite frequently, they'll end up right back in our streets.

SIEGEL: Art Acevedo, chief of the Houston Police Department. Thanks for talking with us today.

ACEVEDO: Thank you. Have a great night. Transcript provided by NPR, Copyright NPR.