Lazcano was born to a poor family on Christmas Day, December 1974, in Apan, Hidalgo, Mexico. He enlisted in the Mexican Army as an infantry soldier at age 17 and was later enrolled in the Grupo Aeromóvil de Fuerzas Especiales (GAFE), an elite special forces team dedicated to combating Mexico’s drug-trafficking organizations. His first military mission took place during the presidency of Ernesto Zedillo, when he was sent along with other GAFE soldiers to put down the armed insurgency in Chiapas. After that, he was moved to northern Mexico as part of a security reinforcement program against the drug trafficking organizations. While serving in the Mexican Army, Lazcano reportedly received training from the Israeli Defense Forces and the United States Army. He acquired training in areas of counter-insurgency and counter-terrorism tactics; sniper techniques; jungle, mountain, desert, naval, and urban warfare; and learned how to use explosives, high-calibre rifles and grenade-launchers.  While traveling through Reynosa, Tamaulipas on 18 February 1998, Lazcano was detained by the Mexican authorities with 325 kilograms of marijuana in his Chevrolet Silverado. During that time, Lazcano was still working as a judicial police officer in Tamaulipas but was also working for the drug lord Osiel Cárdenas Guillén. The federal document does not explain why he was allowed to leave after the narcotics were confiscated, but soon after this incident Lazcano left the military and his duty as a police reinforcement to work full-time for the Gulf Cartel.

He served in the Army for seven years and eventually deserted on 27 March 1998, when he was recruited by Osiel Cárdenas Guillén and Arturo Guzmán Decena to form part of Los Zetas, originally set up by former soldiers of the Mexican Army working on the behalf of the Gulf Cartel. After Cárdenas Guillén was arrested and extradited to the United States in 2007, Los Zetas broke relations with the Gulf Cartel in 2010 and rose to become the strongest criminal organization in Mexico, alongside the Sinaloa Cartel. Lazcano was placed as third in command (Z-3), and after the death of Guzmán Decena (Z-1) in 2002 and the capture of Rogelio González Pizaña in 2004, he became the commander.  Under the tutelage of Lazcano, Los Zetas recruited more gunmen into their ranks, many of them former soldiers of the Mexican military and ex-Kaibiles, the Special Forces squadron of the Guatemalan military, former police officers, and street thugs. Lazcano is also accredited for strengthening Los Zetas and creating regional cells that specialized in other crimes besides drug trafficking. Due to his military background, Lazcano instilled a “military culture” in his squadron, designating new recruits with the titles of “lieutenant” and “commander,” and training them in military tactics.

By 2008, Lazcano forged an alliance with the brothers of the Beltrán Leyva Cartel and with Vicente Carrillo Fuentes of the Juárez Cartel.  Since early 2010, Los Zetas broke relations with their former employers, the Gulf Cartel, causing a violent turf war throughout the border states of Tamaulipas and Nuevo León in northeastern Mexico. The war between these two criminal organizations has left thousands of dead.  Lazcano is suspected of killing hundreds of people, including the journalist Francisco Ortiz Franco, who was assassinated in 2004 in front of his two children as he was leaving a clinic. Lazcano played a particular role in Los Zetas; with his military training, he was able to combine “military precision with stone-hearted criminality.” When he was in power, Lazcano would go with his organization into several regions of Mexico, find out who was in charge of the local kidnapping, human trafficking, and extortion rings, and kill them to take over their business. The rest were then told to join or die.  In its peak era, Lazcano’s criminal empire consisted of about 10,000 gunmen stretching from the Rio Grande all the way into Central America.

Lazcano made a name for himself by decapitating his victims, putting them in acid baths, and for torturing and killing hundreds of people.  When punishing victims, Lazcano became known for using a torture method known as “La Paleta” (‘The Lollipop’), in which victims were stripped naked and brutally beaten with a board. A reporter also recalls that Lazcano reportedly tied a man to a tree and beat him until he broke his legs, and then left him tied to the tree for two or three days until he died. According to the Mexican authorities, Lazcano owned a ranch with several lions and tigers, which he used to get rid of his victims. Lazcano also used effective intimidation kills to keep his subordinates in check. He reportedly dumped his victims (or their children) in large barrels of boiling oil. When he found out that some of his men were stealing from him, Lazcano would force one of them to watch while his henchmen grabbed a 2-by-4 and beat the other to death. When they were dead, the executioner would then cut out the victim’s heart (Lazcano threw the organs away, but other drug lords have forced their guests to eat the organs of the victims). Lazcano also pioneered the decapitation techniques that Los Zetas now employ, and protected witnesses have said that Lazcano would let captured rivals starve to death because he liked to watch the process or that he would let them be eaten by wild animals.

On 7 October 2012, the Mexican Navy responded to a civilian complaint reporting the presence of armed gunmen in Progreso, Coahuila. Upon the navy’s arrival, Lazcano and one gunman -which were inside a white van- opened fire against the marines, triggering a shootout that left Lazcano, his gunman, and one marine dead. The vehicle was found to contain a grenade launcher, 12 grenades, possibly a rocket-propelled grenade launcher and two rifles, according to the Navy. The Navy managed to confirm his death through fingerprint verification and photographs of his corpse before handing the body to the local authorities. However, before the Navy could make an official announcement of his death, several heavily armed and masked gunmen, presumably under orders of Miguel Treviño Morales, stormed the funeral home where his body and that of the other man involved in the shooting lay. Homero Ramos, Coahuila’s state prosecutor, said: “A masked, armed group overpowered the personnel, took the bodies and forced the owner of the funeral home to drive the get-away vehicle.”  At the time of his death, Lazcano was 1.80 m (5 ft 11 in) tall and not 1.60 m (5 ft 3 in), as previously estimated by the authorities.

The Mexican Navy did not identify Lazcano until his body was snatched from the funeral home in Sabinas, Coahuila, a testament that the drug lord had managed to maintain a low-profile behavior. At first, the Navy thought that the two gunmen killed in the shootout were low-level criminals, which explains why they were allowed to be taken to the funeral parlor. Once the bodies were taken, the police matched the fingerprints and photos with those of Lazcano. He was able to be identified because when Lazcano was in the military, his fingerprints were presumably on file; he also spent some time in jail early in his career, and his prints might have been taken there. It is not surprising, however, that Lazcano was not identified immediately, given that there were very few pictures of him. The fact that he had also spent some time in Guatemala and overseas, and that the Navy was responding to a civilian tip that there were armed men at a baseball game, made his finding unexpected. His entourage was also uncharacteristic for a major drug trafficker, although it is quite common for cartel leaders to travel in small groups to avoid attracting unnecessary attention. Unlike other drug traffickers, Lazcano was elusive and turned his back on opulence and power to keep a low-profile status. He was one of the most secretive drug lords in Mexico mainly because he had been trained in military intelligence.