On August 15, 1942, a sixteen-year-old named María de los Ángeles González came to a house in the Tacuba district of Mexico City to meet a young man who had paid for sex. When it was over, Gregorio Cárdenas Hernández strangled her and buried her in his garden. In the following weeks he killed two more sixteen-year-olds who worked as prostitutes, Rosa Reyes and Raquel Martínez de León, and then Graciela Arias Ávalos, nineteen, a fellow chemistry student. The neighbors grew suspicious and told the police. Shortly before officers dug up the bodies, he had himself committed to a psychiatric hospital, and he was arrested there on September 7, 1942.
He was born in Mexico City in 1915 to a family from Veracruz. After a childhood encephalitis infection he behaved abnormally, including being cruel to animals. He won a scholarship from Pemex, the state oil company, to study chemistry at the National Autonomous University. He began visiting prostitutes at fifteen and worried that his constant bedwetting would ruin any lasting relationship. Around 1932 he married Sabina Lara González; the marriage failed after she told people about the bedwetting, and he lost respect for women.
He was the first multiple killer in Mexico to become a national media sensation, and the press named him El Estrangulador de Tacuba, the Tacuba Strangler. Copycat killings were reported, and an illegal pornographic film was made from his story. Accounts of what the courts did with him differ. Some say he was declared insane and held at the La Castañeda asylum; others that he pleaded guilty and was given a life sentence. He was held at the Lecumberri prison, escaped in 1947 to Oaxaca, and was recaptured.
In prison he became a different kind of story. The country's leading psychiatrists and criminologists examined him again and again. He studied psychiatry and law, learned the piano, wrote poetry and three books, married, and had four children with his wife. In 1976 President Luis Echeverría pardoned him, and the interior secretary, Mario Moya Palencia, invited him to address the Congress of the Union, where he was applauded as a great example and a clear case of rehabilitation. That ovation has been argued over ever since.
He finished his law studies and worked as a lawyer. He died in Los Angeles on August 2, 1999. A chance meeting with him in a Mexico City bar inspired Alejandro Jodorowsky's 1989 film Santa Sangre, and he appears as a Lecumberri inmate who has studied law in the Apple TV+ series Women in Blue.