Joaquín Villalón Díez was born on December 11, 1955, in Mérida, Spain. He was born into a poor family. When Joaquín became a young adult, he abandoned his compulsory military service. At some point, he acquired a fake ID. Using this fake identification, he married a woman in Mérida. Together, they had two children. However, Joaquín was not faithful to his wife. He began a relationship with a woman named Francisca "Paquita" Gracía Coca, who was 25 years old at the time.

Joaquín and Paquita decided to get married in August 1981. To prepare for their wedding, they traveled to a town called Les Escaldes in Andorra. On July 22, 1981, Paquita revealed that she was pregnant.

On July 22, 1981, Joaquín Villalón Díez strangled his lover, Francisca 'Paquita' Gracía Coca, after an argument about her pregnancy. He dismembered her body with an electric saw and disposed of the remains in five plastic bags in the Bixerrais River. Shortly after, children playing nearby discovered her remains. The police linked Villalón to the crime due to his proximity to the area and the circumstances surrounding Paquita’s disappearance. He was arrested at a hostel in Spain and sentenced to 17 years in prison.

After serving nine years, Villalón was moved to an open prison in Madrid. There, he began a relationship with a new girlfriend while secretly visiting red-light districts. On September 27, 1992, he went to the apartment of Carmen, a 37-year-old nursing home attendant. Following an argument, he attacked her with an aerosol spray, set her legs on fire, and stole items from her home. Carmen survived initially but later died from her injuries on January 23, 1993.

Two weeks later, Villalón killed another transsexual, Joanna, in her Lavapiés apartment. He knocked her unconscious during a dispute and then drowned her in the bathroom. Afterward, he stole items from her apartment. Friends of Joanna reported her missing after she did not show up for a planned event.

While investigating the deaths of Carmen and Joanna, police accessed the victims’ bank transactions. They identified Villalón after he tried to withdraw money from Joanna’s account. He was arrested and faced trial for murder, robbery, and fraud. During the trial, he claimed to have another personality responsible for his actions. The court found him guilty and sentenced him to 58 years and 10 months in prison, with an additional requirement for psychiatric treatment. He was moved to the Segovia Unit and remained there for 21 years. In 2013, Joaquín Villalón was released due to a change in legal doctrine in Spain.