|Date|| December 24, 1977|
|Weapon(s)|| Shotgun |
Urrego apparently had unsuccessfully tried to court Nubia Grisales, the wife of farmer Raúl Vásquez. Out of revenge he armed himself with a shotgun and a machete, and shortly before midnight ambushed Nubia Grisales and her daughter Piedad in a ravine. After fatally shooting the former and wounding the latter he proceeded to the Vásquez home where he killed six of Grisales' daughters and one of her nephews, as well as a dog.
Urrego was eventually subdued by farmers and villagers who had rushed to the scene to help the family, and handed over to police. The next day an angry mob gathered in front of the prison and threatened to lynch him, but could be deterred after the arrival of police reinforcements. As a consequence the mayor of Angostura proclaimed prohibition for the next 72 hours, and Urrego's whereabouts were kept secret. The burial of his victims on the evening of December 25 was attended by about 7,000 people.
- Nubia Grisales de Vásquez, 38
- Nohra Amparon Vásquez, 11, daughter of Nubia Grisales
- Ruth Myriam Vásquez, 10, daughter of Nubia Grisales
- Dora Yolanda Vásquez, 8, daughter of Nubia Grisales
- Maria del Socorro Vásquez, 6, daughter of Nubia Grisales
- Maria Erlem Vásquez, 5, daughter of Nubia Grisales
- Maria Eugenia Vásquez, 3, daughter of Nubia Grisales
- Hugo Bedoya Vásquez, 12, nephew of Nubia Grisales
Wounded was Piedad Vásquez.