A man who officials say is a top assassin for the cartel once led by Joaquin “El Chapo” Guzman was arrested in Mexico and is the subject of extradition efforts in the United States, officials said Thursday.

Néstor Isidro Pérez Salas, better known as “El Nini,” was arrested at a walled compound in Culiacan, Mexico, on Wednesday afternoon by national security forces, according to an arrest registry.

President Joe Biden, who met with Mexican President Andrés Manuel López Obrador in San Francisco last week, praised the arrest as a result of bravery and U.S.-Mexico cooperation.

“Both our countries are safer with him behind bars and facing justice for his crimes,” Biden said.

U.S. officials allege that Pérez is a top sicario, or assassin, for the murderous Sinaloa Cartel, once led by Guzman, who’s serving a life sentence in Colorado for his role in its trafficking and violence.

They also said he’s the head of security for four of Guzman’s sons — Ivan Archivaldo Guzman Salazar, Jesus Alfredo Guzman Salazar,  Joaquin Guzman Lopez, and Ovidio Guzman Lopez — known as the “Chapitos.”

“He and his security forces murdered, tortured and kidnapped rivals, witnesses, and others who opposed the Chapitos,” U.S. Attorney General Merrick B. Garland said in a statement Thursday.

Wanted in the United States for nearly three years — a $3 million U.S. reward was over his head — Pérez was named in federal charges unsealed in April that allege narcotics, firearms and witness retaliation crimes.

Three of the Chapitos were named in the same case. A fourth, Ovidio Guzman Lopez, pleaded not guilty to a separate-but-identical case in Chicago, where he was being held.

The brothers have all denied the allegations in the federal criminal complaints against them.

The Justice Department has called the four “principal leaders” of the Sinaloa Cartel.