Diego Alexánder Ruiz Restrepo was born on March 14, 1990, in Cali, Colombia. His mother was a teenage parent abandoned by her partner, and Ruiz was raised by his maternal grandparents in the Aguablanca District, one of Cali’s more economically vulnerable sectors. He attended Colegio Carlos Holmes Trujillo, and later worked as a car mechanic for five years—his longest documented employment.

In 2010, his mother emigrated to Chile, and Ruiz followed in 2013, entering the country under a false claim of tourism and remaining there as an undocumented immigrant. He took on several manual labor jobs, mainly in civil construction, but his social and legal stability was fragile due to his immigration status and mounting behavioral problems.

Despite being raised in a Christian household and presenting as a community-oriented man while in Cali, Ruiz’s behavior reportedly shifted after moving to Chile. By 2015, he was living with his sister and brother-in-law in Santiago’s Alameda sector. There, his violent tendencies emerged more openly. He was described as abusive, alcoholic, and aggressive, even stabbing members of his own family—including his mother, sister, grandfather, and stepfather. His sister later obtained a restraining order against him.

Ruiz had a son named Andy from a relationship with an Ecuadorian woman in Chile, but there is little indication that he maintained a stable family life. He became notorious in his neighborhood for regular disputes, making threats, and brandishing knives. He also had multiple criminal records, including theft, threats, and illegal weapon possession, which contributed to his inability to secure legal residency in Chile.

Diego Alexánder Ruiz Restrepo's murder spree began on March 7, 2020, when he killed his first known victim, 72-year-old Víctor Olegario Allende Salas. Ruiz's next murders took place on November 1, 2020, when he killed Colombian immigrant Carlos Andrés Rivas Angulo, 35. Later that day, he also murdered 64-year-old Guido Hernán Gallardo Contreras, who was homeless.

On November 8, 2020, Ruiz committed four more murders in a single night. His first victim that night was 49-year-old Luis Marcelo Romero Jeria, also homeless. Following him was 57-year-old Marcia Margot Tapia Loncón, a woman who struggled with alcoholism and schizophrenia. Next, he killed 40-year-old Leónidas Vicente Panez Fierro, a former police officer who was living on the streets. The last victim, 32-year-old Rodrigo “Che” Manino Carmona was an Argentine immigrant.

On August 3, 2020, Ruiz threatened another individual, Óscar P., with a knife, claiming he had killed many before him. On November 8, 2020, he also attacked Pedro Manuel Bustamante Babbonney, who survived the attack.

Investigators linked Ruiz to at least 20 other deaths. They studied his behavior patterns and reviewed security camera footage that captured his movements. He was arrested on November 9, 2020, and charged with multiple murders. Over time, he became connected to several crimes beyond those confirmed.

By January 2021, he was in preventive detention. In July 2023, Ruiz was sentenced to life imprisonment, eligible for parole after 40 years. He primarily targeted homeless individuals, as they often went unnoticed by families. His deadliest night involved attacking five people in just 70 minutes, leading to four deaths.