While in Los Zetas, Lorméndez Pitalúa had worked on several assignments directed by Guzmán Decena.
On 20 June 2001, he was part of an assault team of twenty-five Zetas' members that raided the Tamaulipas State Police headquarters in Matamoros to free José Ramón Dávila López ("El Cholo"), a high-ranking Zetas' member from jail.
According to eye-witnesses, Lorméndez Pitalúa and his associates stormed the police installation wearing black uniforms and sporting AK-47s and AR-15s, and used a tear-gas grenade launcher to rescue their comrade.
Although Los Zetas were successful in rescuing Dávila López, they suffered a few losses: Zetas' member Hugo Ponce Salazar ("Z-4") was arrested alongside former Matamoros Municipal Police officer José Octavio Garza Garza and José Guadalupe Vidaña Triana.
In retaliation for the losses inflicted by security forces and the increased police activity in their territory, Los Zetas reportedly responded less than three weeks later by murdering state police chief Jaime Yañez Cantú and his driver Gerardo Gascón Soltero in a drive-by shooting on 9 July 2001 in Matamoros.
Dávila López began working under Lorméndez Pitalúa and Heriberto Lazcano Lazcano as one of the cartel's lead assassins.

On 14 March 2003, Cárdenas Guillén was arrested by the Mexican Army in Matamoros.
His arrest dealt a huge blow to the Gulf Cartel and forced several cartel members to go into hiding temporarily.
From March to August, Gulf Cartel leaders Jorge Eduardo Costilla Sánchez ("El Coss") and Gregorio Sauceda Gamboa ("El Caramuela") hid and continued to operate and maintained a low profile, but Lazcano Lazcano took over some of the cartel's operational activities and helped them regroup.
During that period, Lorméndez Pitalúa was based out of Nuevo Laredo and reportedly operated on both sides of the U.S.-Mexico border.
The U.S. Federal Bureau of Investigation (FBI) had information that Lorméndez Pitalúa and other Zetas members lived in Laredo, Texas.
He was in charge of taking control of the territory from other gangs that operated in the area: Los Cachos, Los Texas and Flores Soto.
His main objective, however, was to help the Gulf Cartel and Los Zetas in their gang war against the Sinaloa Cartel; rival gangsters Eloy Treviño García and Edgar Valdez Villarreal ("La Barbie") opposed Lorméndez Pitalúa's expansionist plans and ordered their associates to wage a war against them.
Lorméndez Pitalúa's campaign against the Sinaloa Cartel also extended to other parts of Tamaulipas, Guerrero, Michoacán, Nuevo León and Mexico City.
He had the support of cartel members Mateo Díaz López, Raúl Lucio Hernández Lechuga ("El Lucky"), Héctor Manuel Sauceda Gamboa ("El Karis"), Iván Velázquez Caballero ("El Talibán") and Miguel Treviño Morales ("Z-40").

In late 2003, Zetas member Flavio Méndez Santiago ("El Amarillo") and Lorméndez Pitalúa were sent to Michoacán to combat the rival forces of the Milenio Cartel and attempt to take over their territory.
The rival Beltrán Leyva Cartel also operated in the area and Los Zetas was in charge of eliminating their influence in Zihuatanejo and Acapulco.
Lorméndez Pitalúa was appointed as the head of Los Zetas in Michoacán by Lazcano Lazcano during a meeting held in Valle Hermoso, Tamaulipas.
While in Michoacán, Lorméndez Pitalúa became a close ally of Carlos Rosales Mendoza ("El Tísico") and Servando Gómez Martínez ("La Tuta"), who headed the Michoacán-based La Familia Michoacana criminal group.
As well as from working against the Milenio Cartel, Lorméndez Pitalúa was also responsible for establishing connections with authorities to help Los Zetas gain information from officials working against them.
He had local authorities from Michoacán and Guerrero providing him with information and protection from the local police.
Public officials were paid by Los Zetas to allow them to operate freely in the area without being arrested.
Lorméndez Pitalúa paid US$50,000 and more to these officials.
He also bought uniforms and weapons for the police.
In Michoacán, Lorméndez Pitalúa had two former Kaibiles (special f
While in Los Zetas, Lorméndez Pitalúa had worked on several assignments directed by Guzmán Decena. On 20 June 2001, he was part of an assault team of twenty-five Zetas' members that raided the Tamaulipas State Police headquarters in Matamoros to free José Ramón Dávila López ("El Cholo"), a high-ranking Zetas' member from jail. According to eye-witnesses, Lorméndez Pitalúa and his associates stormed the police installation wearing black uniforms and sporting AK-47s and AR-15s, and used a tear-gas grenade launcher to rescue their comrade. Although Los Zetas were successful in rescuing Dávila López, they suffered a few losses: Zetas' member Hugo Ponce Salazar ("Z-4") was arrested alongside former Matamoros Municipal Police officer José Octavio Garza Garza and José Guadalupe Vidaña Triana. In retaliation for the losses inflicted by security forces and the increased police activity in their territory, Los Zetas reportedly responded less than three weeks later by murdering state police chief Jaime Yañez Cantú and his driver Gerardo Gascón Soltero in a drive-by shooting on 9 July 2001 in Matamoros. Dávila López began working under Lorméndez Pitalúa and Heriberto Lazcano Lazcano as one of the cartel's lead assassins.
On 14 March 2003, Cárdenas Guillén was arrested by the Mexican Army in Matamoros. His arrest dealt a huge blow to the Gulf Cartel and forced several cartel members to go into hiding temporarily. From March to August, Gulf Cartel leaders Jorge Eduardo Costilla Sánchez ("El Coss") and Gregorio Sauceda Gamboa ("El Caramuela") hid and continued to operate and maintained a low profile, but Lazcano Lazcano took over some of the cartel's operational activities and helped them regroup. During that period, Lorméndez Pitalúa was based out of Nuevo Laredo and reportedly operated on both sides of the U.S.-Mexico border. The U.S. Federal Bureau of Investigation (FBI) had information that Lorméndez Pitalúa and other Zetas members lived in Laredo, Texas. He was in charge of taking control of the territory from other gangs that operated in the area: Los Cachos, Los Texas and Flores Soto. His main objective, however, was to help the Gulf Cartel and Los Zetas in their gang war against the Sinaloa Cartel; rival gangsters Eloy Treviño García and Edgar Valdez Villarreal ("La Barbie") opposed Lorméndez Pitalúa's expansionist plans and ordered their associates to wage a war against them. Lorméndez Pitalúa's campaign against the Sinaloa Cartel also extended to other parts of Tamaulipas, Guerrero, Michoacán, Nuevo León and Mexico City. He had the support of cartel members Mateo Díaz López, Raúl Lucio Hernández Lechuga ("El Lucky"), Héctor Manuel Sauceda Gamboa ("El Karis"), Iván Velázquez Caballero ("El Talibán") and Miguel Treviño Morales ("Z-40"). 
In late 2003, Zetas member Flavio Méndez Santiago ("El Amarillo") and Lorméndez Pitalúa were sent to Michoacán to combat the rival forces of the Milenio Cartel and attempt to take over their territory. The rival Beltrán Leyva Cartel also operated in the area and Los Zetas was in charge of eliminating their influence in Zihuatanejo and Acapulco. Lorméndez Pitalúa was appointed as the head of Los Zetas in Michoacán by Lazcano Lazcano during a meeting held in Valle Hermoso, Tamaulipas. While in Michoacán, Lorméndez Pitalúa became a close ally of Carlos Rosales Mendoza ("El Tísico") and Servando Gómez Martínez ("La Tuta"), who headed the Michoacán-based La Familia Michoacana criminal group. As well as from working against the Milenio Cartel, Lorméndez Pitalúa was also responsible for establishing connections with authorities to help Los Zetas gain information from officials working against them. He had local authorities from Michoacán and Guerrero providing him with information and protection from the local police. Public officials were paid by Los Zetas to allow them to operate freely in the area without being arrested. Lorméndez Pitalúa paid US$50,000 and more to these officials. He also bought uniforms and weapons for the police. In Michoacán, Lorméndez Pitalúa had two former Kaibiles (special f
Omar Lorméndez Pitalúa