Texas native Gabriel Cardona and his crew of teen assassins were busted by the feds just before importing the murderous Mexican drug wars to the streets of Laredo.

The story begins with law enforcement success: The federal Drug Enforcement Administration, in the mid-’90s, shut down the cocaine trafficking route between South Florida and Colombia.

The result? Some 90% of the cocaine and much of the methamphetamine that reached the U.S. was instead now funneled through Mexico.

The most lucrative of the drug crossings became Laredo, Texas, one of the nation’s poorest cities, sitting across the Rio Grande from the Mexican city of Nuevo Laredo.

In 2004, Nuevo Laredo fell under the control of Los Zetas — the vicious enforcement arm of the Gulf Cartel — and its regional commander Miguel (Forty) Trevino.

Trevino freely admitted to more than 800 murders, including one where he killed a man — and then forced the victim’s brother to dine on his slain sibling’s brains.

He and his well-trained, black-clad soldiers were engaged in a corpse-strewn battle with the Sinaloa Cartel for control of Laredo.

Colombian mercenaries taught the recruits combat skills — but the real test for the newbies was ahead: hands-on murder.