Alfredo Beltrán Leyva was arrested on January 21 in Culiacán, capital of the Mexican state of Sinaloa. The circumstances of his arrest lived up to his high standing in Mexico’s criminal underground, caught, as he was, driving a BMW S.U.V. in which federal police found eight pistols, an AK-47 assault rifle, and two suitcases containing about $900,000 in cash. Until his arrest, Beltrán Leyva was a top lieutenant in what may be the most profitable and far-reaching drug-trafficking organization in the world: the Sinaloa cartel, presided over by Joaquín Guzmán, often referred to as Mexico’s Pablo Escobar. Beltrán Leyva—known as El Mochomo after a vicious night-crawling ant—is thought by police to have been a Guzmán favorite, carrying out multiple murders while moving tons of drugs and millions of dollars for him.

The day after Beltrán Leyva’s arrest, federal police raided two mansions in Mexico City. They nabbed 11 members of his hit squad and discovered an arsenal including dozens of high-powered rifles, fragmentation grenades, thousands of rounds of ammunition, and Kevlar vests stamped FEDA. The police believe this stands for Fuerzas Especiales de Arturo, or Arturo’s Special Forces, a reference to Alfredo’s older brother, who ranks even higher in Guzmán’s organization.

One of the pistols taken from Beltrán Leyva’s truck was an American-built, silver-plated Colt .38 Super, long the preferred firearm of aesthetically inclined narco­traficantes. Originally made in the 1920s, the .38 is an iconic gun, with a sleek rectangular barrel, angled handle, and forward-thrusting look that give it a certain élan. Custom models like Beltrán Leyva’s can go for $10,000. A monogrammed, emerald-encrusted .38 Super that belonged to one infamous drug lord now resides in a Mexican museum. (View slideshow.)

Guns are nearly impossible to buy legally in Mexico, so when the Beltrán Leyva haul was brought into federal police headquarters in Mexico City...