Gregorio Cárdenas Hernández was born in 1915 in Mexico City to a family originally from Veracruz. As a child, he suffered from encephalitis, which led to behavioral issues, including cruelty to animals and social withdrawal. Despite these challenges, he was intellectually gifted and earned a scholarship from Pemex to study chemistry at the National Autonomous University of Mexico (UNAM).

Cárdenas married Sabina Lara González around 1932, but the marriage was short-lived. He harbored resentment towards women, which may have stemmed from personal insecurities and his troubled relationships.

Between August and September 1942, Cárdenas committed a series of murders in the Tacuba neighborhood of Mexico City. His victims were:​
María de los Ángeles González, 16, murdered on August 10
Raquel Martínez León, 14, murdered on August 23
Rosa Reyes Quiroz, 16, murdered on August 29
Graciela Arias Ávalos, 21, murdered on September 2

Cárdenas lured these young women to his home, where he strangled them and buried their bodies in his garden. After the disappearance of Graciela Arias Ávalos, suspicions arose, leading to an investigation. On September 7, 1942, Cárdenas was arrested at a psychiatric hospital where he had admitted himself, claiming insanity.

He was initially confined to La Castañeda Psychiatric Hospital but escaped in December 1946. He was recaptured shortly thereafter and transferred to Lecumberri Prison. During his incarceration, Cárdenas pursued studies in psychiatry and law, wrote poetry, and even married, fathering four children.

In 1976, after 34 years in custody, President Luis Echeverría granted him a pardon. Cárdenas was celebrated as a rehabilitated individual, even delivering a speech before the Mexican Congress. He completed his law degree in 1985 and practiced law until his death from natural causes in Los Angeles on August 2, 1999.