Efraín Sarmiento Cuero was born on 20 May 1996 in Policarpa, Nariño (Colombia). Public reporting on his youth is limited in detail; however, the criminal record that emerges in court files and press coverage shows a rapid escalation from interpersonal violence to sexual violence and homicide beginning in 2017. By April 2017, Sarmiento had become linked to the first confirmed homicide attributed to him — the rape and strangling of Cristiana Mendoza Maya in a hotel room in Cali. Authorities later tied him to a second fatal hotel attack in November 2018 in the Nariño region (the killing of Jacqueline Muñoz Ojeda), after which he was arrested, tried and convicted for those crimes. Court records and news outlets report he received lengthy custodial sentences (34 years, 8 months; and 20 years, 8 months for the separate murders). 

Following conviction, Sarmiento was moved to the El Barne maximum‑security prison in Cómbita, Boyacá. While incarcerated he was reportedly permitted limited use of social media and dating sites, through which he cultivated a long‑distance relationship with Merly Andrea Rengifo Cuadros, a 33‑year‑old housekeeper from Cali and mother of two. Rengifo visited him regularly for conjugal visits after accepting his representations that he was innocent and the target of an extortion plot. Over time, prison staff say Sarmiento became increasingly controlling — demanding real‑time location photos and checking who she was with — a dynamic that culminated in the fatal violent episode during a conjugal visit in May 2023.

In April 2017, Sarmiento met Cristiana Mendoza Maya and took her to a hotel in Cali. Hotel staff found Mendoza’s body later; official autopsy reports cited rape, strangulation and blunt force injuries. Investigators concluded she had been physically beaten before being strangled. That homicide remained under investigation until Sarmiento’s later arrest and linkage to subsequent crimes.

On 3 November 2018 (reported date), Sarmiento went with Jacqueline Muñoz Ojeda to a hotel in the municipality of Policarpa / Pasto. An argument reportedly escalated; Sarmiento beat and then strangled her with a belt. He was arrested shortly afterward and investigators connected him with the 2017 Cali homicide as well. He was ultimately convicted for both homicides and received the long combined prison terms reported in Colombian media.

While serving his sentences at El Barne in Cómbita, Sarmiento used permitted internet/dating access to form a relationship with Merly Andrea Rengifo Cuadros, a woman from Cali who visited monthly. Rengifo reportedly believed Sarmiento’s claims of wrongful conviction. During the relationship Sarmiento demonstrated escalating jealousy and control, asking for constant proof of her whereabouts. On Mother’s Day, 14 May 2023, during a conjugal visit, staff later discovered Rengifo inside Sarmiento’s cell at 10:05 a.m., with extensive bruising and a fatal neck wound; she had been cut in the throat. INPEC personnel and prosecutors reported the victim had bruises to the legs, cheeks, chest and neck, and that Sarmiento later said he wounded her to signal that “she had an owner.” Sarmiento accepted responsibility and was charged with femicide; the Attorney General sought stricter security measures and reclassification of his detention status as “too dangerous” for ordinary housing. The case was pending additional proceedings at the time of reporting.

Sarmiento was already serving a combined long custodial sentence for the earlier murders (media report: 34 years, 8 months for one murder and 20 years, 8 months for the other). After the 2023 prison killing he was formally charged with femicide; Colombian prosecutors presented him before a judge and requested enhanced security and classification due to the severity and brazenness of the prison murder (committed during a conjugal visit). As of the last published reports, he remained in custody in Boyacá awaiting the next phase of prosecution for the new charge.