The former head of the FBI's criminal investigative division, Chris Swecker, said the notorious MS-13 gang from Central America isn't looking for wealth but is driven only by hate, and a desire to spread violence and destruction.

"They haven't changed much since 2004, 2005. Their hallmark is just knuckle-dragging, senseless violence -- not to gain money, like the La Cosa Nostra or for a profit motive, but just for respect and turf," he said. "They have no purpose really, other than just organization around violence."

The former head of the FBI's first MS-13 tass force gave some background on how the gang was formed and said despite managing drug and prostitution rings, they usually don't flash their cash out in public.

He also said the MS-13 members living in America are lower on the totem pole of the organization, referring to them as "thugs" and claimed they aren't fueled by ideology.

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"They stem from El Salvador and Honduras, mainly El Salvador, where there was a civil war back in the '70s. And they sort of carried that on, by forming up this gang in Los Angeles. One for protection but two, to sort of continue the cause. But they really don't have any profit motive," he said.

"They're into extortion, they're into drugs and prostitution but you won't see them driving fancy cars, gathering in a lot of wealth. They're a different organization in El Salvador. They're more of a paramilitary organization there. Here they're just a bunch of thugs."

Swecker said they tend to target those in their own community and claimed there about 10,000-20,000 MS-13 members wreaking havoc in the United States today.

He blamed the lack of security at the southern border for their entry and said it's hard to pin down exactly how many have come and gone in recent years.

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"They target immigrant communities. They form up around immigration communities... Most of them are illegal. They're in and out of the country all the time. But for whatever reason, they tend to prey on their own communities, which is insidious," he said.

"What I can tell you is the numbers are a little bit fuzzy. There's about 10,000 hard-core gang members in the United States, maybe 20,000 associates of MS-13, and they come and go so frequently through our porous borders. They mingle in with the caravans. They've associated themselves with the Sinaloa cartel. They're soldiers for the Sinaloa cartel. They're into human trafficking. They're in and out so often, it's very difficult to pinpoint how many there are floating across the border at any given time."