Born in Matamoros, Tamaulipas, Antonio initially worked as a car washer at a local police station with his brother Osiel Cárdenas Guillén, former leader of the cartel.

Back in Mexico, his brother Osiel was the Gulf Cartel's main leader and had created a paramilitary squad known as Los Zetas, formed by soldiers who left the Mexican military.

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.

[6][7] 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.

[8][9] Inside the domicile, the US authorities discovered "cash, numerous vehicles, cocaine, marijuana, firearms and one 1996 Sea Doo Bombardier with expired Florida registration.

[10][11] Ten months later in 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.

[13][14] In 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.

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.

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.

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.

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.

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.

[28] 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.

[7] 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.

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.

[34][35] 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.

[37] 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.

[41][42][43] Antonio Ezequiel was killed by the Mexican Navy at around 6:00 p.m. in downtown Matamoros on 5 November 2010, but the roadblocks set by organized crime continued throughout the rest of the day.

The drug lord had reportedly called for backup when he was surrounded by the Navy, but when he was killed, his reinforcements from Reynosa, Tamaulipas (which consisted of over 80 SUVs filled with gunmen) dispersed.

Law enforcement officials confirmed that an armed confrontation broke out between gunmen of Los Zetas and the Gulf Cartel in Ejido Las Rusias neighborhood, and shootouts in the Lauro Villar and Roberto Guerra avenues in Matamoros.

With Antonio Ezequiel dead, Los Zetas celebrated the death of their rival's leader by hanging banners at pedestrian bridges in several cities in northeastern Mexico, where they mocked his brother Osiel and the Gulf Cartel.

[47] Among the most intense battles between the Gulf Cartel and Los Zetas following the death of Antonio Ezequiel occurred in Ciudad Mier, Tamaulipas, a small, painteresque town on the U.S.-Mexico border.

[48][49] The Mexican government responded to the citizens' plea by sending reinforcements to restore order because the violence had been "non-stop in Ciudad Mier since [Antonio Ezequiel's] death.

[58] Stratfor and border security expert Sylvia Longmire, however, believed that Antonio Ezequiel's death was not going to drastically alter the dynamics of the criminal world, and that his absence may possibly bring some level of relative peace in the Tamaulipas area.

[59][60] The intelligence agency stated that Antonio Ezequiel was only a leader in the Gulf Cartel because of his brother Osiel; Costilla Sánchez, on the other hand, was the one who actually controlled the day-to-day operations.

It was rumored that the drug lord was hot-tempered and lived an outlandish lifestyle, and that many commanders within the Gulf Cartel believed in more than one occasion that his position as leader threatened the whole organization.

[60][61] Longmire believed that Los Zetas would move into Reynosa and Matamoros shortly after the drug lord's death to "test the waters", but she stated that the Gulf Cartel, under the command of Costilla Sánchez, stood a chance to fight them off and continue its illicit activities.

When a drug baron is arrested or killed, the criminal organization may experiences a leadership void, which leads to infighting for succession, possible fragmentation, and new competition from other crime syndicates.

[63][64] Antonio Ezequiel commanded an elite enforcer group known as Los Escorpiones (The Scorpions), which served as his private army during the 5 November 2010 shootout in Matamoros that resulted in the drug lord's death.

[76] The act prohibited U.S. citizens and companies from doing any kind of business activity with him, and virtually froze all his assets in the U.S.[77] A character loosely based on Antonio Cárdenas Guillén was featured in the 2017 TV series El Chapo.