(NewsNation) — Few drug lords have attained the notoriety that El Chapo has.

For years, he helmed the Sinaloa Cartel — building a drug trafficking empire with a larger footprint in the United States than anyone else.

El Chapo is now serving a life sentence in the U.S., and the takedown created a power vacuum in Mexico. But once the dust settled, four men rose to the top of the organization: Ivan Guzman Salazar, Alfredo Guzman Salazar, Joaquin Guzman Lopez, and Ovidio Guzman Lopez. All four, known as “Los Chapitos,” or “The Little Chapos,” are sons of the former boss.

Jack Riley was the deputy administrator of the Drug Enforcement Agency who led the charge to bring El Chapo down in 2016.

“For me, it was the Super Bowl,” Riley recalled. “It was everything we work for.”

According to Riley, Los Chapitos are every bit as vicious as their father was at the height of his career — “willing to kill anybody to stay in business.”

They even have a track record of feeding their enemies “dead or alive” to tigers just to send a message, according to an unsealed indictment from the Southern District of New York.

What Los Chapitos are most well known for, however, is overhauling the cartel’s drug operation — shifting it from methamphetamine, heroin and cocaine to fentanyl.

“Five years ago, I had never even heard of fentanyl, and now it’s the No. 1 killer,” San Diego County Supervisor Jim Desmond said.

In 2016, Customs and Border Protection seized 564 pounds of fentanyl. That number has since skyrocketed to 17,200 pounds in the past seven months alone — a roughly 3,000% increase in just over six years.

While multiple cartels are vying for the American market, the latest analysis from the DEA suggests the Sinaloa Cartel has far and away the most control.

“If Sinaloa in its business operation was a legit company, it would be one of the largest corporations and most successful in the world,” Riley said.

Earlier this year, Ovidio Guzman Lopez, one of the four sons, was captured in a shootout that left at least 29 dead.

Still, the other three remain at large. Riley is now out of the game as a DEA administrator, but fears if left unchecked, Los Chapitos will continue to expand the operation and the fentanyl problem will get much worse.

“I’ve always said to our European counterparts, it’s coming your way,” Riley said. “The real key here for Sinaloa is they have unlimited resources, and they make up the rules.”