Antonio Ezequiel Cárdenas Guillén was born on 5 March 1962 in El Mezquital ranch in the border city of Matamoros, Tamaulipas, Mexico. As a teenager, Antonio Ezequiel and his brother Osiel earned their living by washing cars at the headquarters of the Federal Judicial Police in their hometown. By the late 1980s, Cárdenas Guillén started his criminal career under the Gulf Cartel, where he became a high-ranking leader and commanded organized crime activities and drug trafficking in Matamoros. His contact with the police in Matamoros marked the life of the Cárdenas Guillén clan; federal reports of the Procuraduría General de la República (PGR) suggest that the drug lord had solid business relations with police and military men. Witnesses indicate that Antonio frequented public places in Matamoros, Reynosa, Ciudad Victoria, and other cities in the state of Tamaulipas surrounded by a number of municipal and state police officers, whose superiors have allegedly remained loyal to the Gulf Cartel for over half a century. His henchmen reportedly wore bullet-proof vests with the Spanish insignias for the Gulf Cartel (Cártel del Golfo – C.D.G.) embellished across their chests. Although some of Antonio Ezequiel’s men were reported to have worn military garbs while on duty, their uniforms have also become more subtle with time. For example, some Gulf Cartel gunmen wear tennis shoes of the same color, caps with the logo “CDG–TT” (Gulf Cartel–Tony Tormenta), or trucks emblazoned with the same logo to help them distinguish themselves from rival gangs.

A decade before ascending in the Gulf Cartel leadership rankings, Cárdenas Guillén avoided arrest by FBI and DEA agents in 1998, after they raided his home in Houston, Texas. The federal agents saw the drug lord leave, but they decided to pursue a search warrant than to chase him, given the activity in the neighborhood, the amount of cars at the parking lot near his house, and the lack of sufficient agents in the operative. Inside the domicile, the US authorities discovered “cash, numerous vehicles, cocaine, marijuana, firearms and one 1996 Sea Doo Bombardier with expired Florida registration.” In 1998, the federal agents knew little about Cárdenas Guillén and the criminal organization he worked for. The FBI later closed the investigation in February 1999 due to the drug lord’s fugitive status, his local indictments, and the lack of information available in the Houston jurisdiction. Ten months later on November 1999, the Cárdenas Guillén surname started to gain momentum when Antonio Ezequiel’s brother Osiel and several of his gunmen stopped two US federal agents at gunpoint in the streets of Matamoros. After a tense standoff, the agents convinced Osiel to let them go.  Under orders of his brother Osiel, Antonio Ezequiel ordered the drug lord Gregorio Sauceda Gamboa (alias El Goyo) and his henchmen to execute 6 prison guards in Matamoros on 20 January 2005, reportedly as a reprisal for Osiel’s treatment at Altiplano prison. Their corpses were discovered inside a Ford Explorer near the Matamoros federal prison. On May 2005, he commanded a battalion of over 100 Zeta members to fight off Los Pelones, an enforcer group working for the Beltrán Leyva Cartel, in the state of Guerrero.

In 2003, Osiel was arrested in Matamoros following a shootout with the Mexican military, and was extradited to the United States in 2007. In exchange for a life sentence, Osiel cooperated with the U.S. authorities by supplying information on the workings of the Gulf Cartel and Los Zetas. When Osiel was arrested, Antonio Ezequiel inherited the Gulf Cartel along with Jorge Eduardo Costilla Sánchez, a former policeman in Matamoros. He and other Gulf Cartel leaders were responsible for trafficking multi-ton drug shipments of cocaine and marijuana from Mexico to the United States. Antonio Ezequiel received a federal indictment in 2008 in the District of Columbia for drug trafficking violations. He also directed the flow of narcotics through land, sea, and air from Venezuela and Colombia to Guatemala and the U.S-Mexico border. When Osiel was imprisoned, several high-ranking lieutenants in the Gulf Cartel got together to appoint leaders and their turfs. According to the declarations of Zeta leader Mateo Díaz López (alias Comandante Mateo), Antonio Ezequiel was given the turf of Matamoros, one of the leading smuggling routes for the cartel. But Antonio Ezequiel never had the edge; one of his most trusted men, Ramiro García Hernández (alias El Mati), was arrested in 2004. Deemed inexperienced, Costilla Sánchez, Lazcano, and high-ranking leader Víctor Manuel Vázquez Mireles (alias El Meme Loco) moved Antonio Ezequiel to command the Gulf Cartel in Cancún. But after failing to meet the Gulf Cartel’s demands, he was replaced.

With Osiel imprisoned, however, Costilla Sánchez was deemed more powerful than Antonio Ezequiel. According to the declaration of the imprisoned drug lord Jaime González Durán (alias El Hummer), Osiel appointed Costilla Sánchez while still in prison, and left his brother Antonio as a representative of his clan. Heriberto Lazcano Lazcano, too, was part of the first tier circle, but he headed Los Zetas, while the other two commanded the Gulf Cartel directly. The triumvirate of Antonio Ezequiel, Costilla Sánchez, and Lazcano controlled the flow of narcotics from the southern state of Quintana Roo to the northern Tamaulipas state. Although initially part of a single command structure during the Osiel era, members within Los Zetas and the Gulf Cartel began to follow orders of their respective commanders. During the 1990s and early 2000s, the Gulf Cartel “operated with a certain structure that allowed for rivalries among lieutenants to exist without affecting the organization as a whole”. But with Osiel’s absence, several top leaders within the cartel fought to take control of the leadership void. This eventually resulted in the split of the Gulf Cartel and Los Zetas in early 2010, prompting daily shootouts and killings from both fronts. The conflict between both groups triggered in Reynosa, Tamaulipas in January 2010, when Samuel Flores Borrego of the Gulf Cartel killed a Zetas leader. When the fighting broke out in Reynosa, Antonio and Los Escorpiones, his private army, made their way into Valle Hermoso, Tamaulipas and took the city from Zetas’s control. Several municipal and transit police officers – who were on Los Zetas’s payroll – were hung from light poles as a message from Antonio to his rivals.

For at least six months, the Mexican Armed Forces were trying to hunt down Antonio Ezequiel, nearly capturing him in two occasions. The drug lord managed to avoid capture in several occasions by relying on the armed squadron known as Los Escorpiones (The Scorpions), which served as his private army. Among the first operations to capture the drug lord occurred on 31 March 2010, when the Mexican military confronted Antonio Ezequiel’s bodyguards at Tres Culturas neighborhood in Matamoros. On 7 April 2010, there were two shootouts in Matamoros between Mexican marines and members of the Gulf Cartel. The intelligence information collected in these shootouts allowed the Mexican Armed Forces to locate the domicile of Antonio Ezequiel on 14 September 2010 at Fraccionamiento Río in Matamoros. But heavily armed gunmen of the Gulf Cartel intercepted the raid and protected their leader, who escaped in an armored vehicle. Two military men were killed in the operation, but the government managed to gain more information on the logistics of the inner circle of Antonio Ezequiel. On 1 November 2010, the Mexican authorities learned once again that Antonio Ezequiel was spending the night in a safe house at the Expo Fiesta Oriente neighborhood in Matamoros. But before the authorities got to the location, the drug lord left and avoided his capture.

Antonio Ezequiel was killed on 5 November 2010 following an eight-hour shootout between gunmen of the Gulf Cartel and soldiers of the Mexican Navy in his hometown of Matamoros, Tamaulipas. Government sources claimed that this operation—where more than 660 marines, 17 vehicles, and 3 helicopters participated—left 10 dead: three marines, one soldier, four Gulf Cartel gunmen, journalist Carlos Alberto Guajardo Romero, and the drug lord Antonio Ezequiel. The shootout began at around 10:00 a.m. and extended to 6:00 p.m., when Antonio Ezequiel and gunmen of his inner circle were killed. The intensity of the shootout forced the temporary closure of the international bridges that connect Matamoros with the US border city of Brownsville, Texas, along with the University of Texas at Brownsville, which sits on the edge of the Rio Grande River. The day light clashes generated a wave of panic among the citizens of Matamoros, who turned to social networks like Twitter and Facebook to report the violence. “Shelter, everyone! Don’t leave your houses please. Pass the word,” read one tweet. People hid inside their homes or in windowless offices, sometimes peaking to see the cartel mayhem. Witnesses reported seeing military men carrying guns, and armed Gulf Cartel members in their own military uniforms. Power went out in several parts of downtown Matamoros, where most of the heavy gun fight took place. Communication equipment, like cellphones and radios, were not working. Gulf Cartel gunmen hijacked several buses to block roads all across the city to prevent the mobilization of the Mexican Armed Forces. Hovering helicopters from the Navy shot down at Antonio Ezequiel’s henchmen. “The city was paralyzed,” said an office worker who hid for hours inside a building. “It was a nightmare. It went on and on.” News reports described 5 November 2010 as one of Matamoros’s bloodiest days.

When the military arrived at Antonio Ezequiel’s location in downtown Matamoros to arrest him at 3:30 p.m., his gunmen tried to protect the drug lord by launching several grenades and shooting at the officers. At the scene, at least 300 grenades were detonated, and gunfire perforated the building where Antonio Ezequiel hid. Gulf Cartel snipers, who hid in the rooftops of the drug lord’s hiding place, shot at the Mexican marines, who later entered the building and killed Antonio Ezequiel and several bodyguards of his inner circle. Contrary to government reports, the newspapers The Brownsville Herald and The Monitor, which are based in the Rio Grande Valley, reported that at least 47 dead from the shootings that broke out on 5 November 2010 in Matamoros. According to an anonymous source inside of Mexican law enforcement, at least 30 people had been killed by noon; by the afternoon, 17 had been gunned down near the Matamoros city hall in the downtown area by grenades and heavy-calibre gunshots. Other sources varied in their countdown. Some local sources suggest that 55 or more people had been killed in the shootout. Comments left by readers at The Brownsville Herald and its sister page El Heraldo reported at least 70 dead. Although not officially confirmed, an anonymous law enforcement officer, KVEO-TV, and several online sources and witnesses mentioned that the two-day death toll in Matamoros may have “easily passed” 100. However, the exact figures of those killed in Matamoros are virtually unknown.