His modus operandi consisted of ambushes on sidewalks, estates and highways, where he kidnapped and murdered law enforcement officials (such as soldiers and policemen), civilians, peasants and even minors.
At the time, he was known by the alias Desquite, because he exacted revenge for the murders of his father and brother, as well as suffering from the dispossession of his property.
"[4] Aranguren's first recorded criminal activity was in 1956, when he ambushed a truck from a tobacco company called 'Compañía Colombiana de Tabaco'.
In December, after confronting and surrounding a police checkpoint in Mariquita, Aranguren murdered the four policemen assigned to the area.
According to the information, Aranguren kidnapped a child, killing him in a particularly cruel manner by piercing his heart with a knife and later dismembering the corpse in eight pieces, which he then buried in a mass grave.
Colombian army commandos and police were alerted from an anonymous tipster, and quickly prepared to enter the premises after verifying that it was indeed the suspect.
After this, the entire Colombian army repeatedly threw grenades at the farm, in order to prevent any other associate of Aranguren from escaping alive.
He was accompanied by three accomplices: Alfonso "Pata de Chivo" Parra, Gustavo "Veneno" Ávila and Alberto "Peligro" López, all of whom were armed.