Andrés Ulises Castillo Villarreal was born in 1980 in Chihuahua City, Chihuahua, Mexico. Details about his early life are scarce, but he was known to be a small-time drug dealer, commonly referred to as a "narcomenudista." This occupation allowed him to interact with young men who were methamphetamine users, whom he later targeted as his victims.

Between 2009 and 2015, Castillo Villarreal orchestrated a series of heinous crimes in Chihuahua City. He would lure young male methamphetamine users with the promise of free drugs, leading them either to secluded areas on the city's outskirts or to his own residence. Once there, he would intoxicate them further, incapacitate them by striking their heads with blunt objects, sexually assault them, and ultimately kill them by inflicting fatal head injuries. He then dismembered their bodies using a coping saw—a consistent tool in his crimes. The dismembered remains were transported in a wheelbarrow and disposed of in vacant lots, often partially hidden or buried. Notably, he left toys beside the mutilated bodies as a macabre signature. ​

The investigation into Castillo Villarreal's crimes intensified following the discovery of dismembered human remains in November and December 2015. On January 6, 2016, authorities arrested him in connection with these murders. Subsequent investigations revealed a third victim buried in one of the rooms of his residence. He was also charged with sexually assaulting two other men. During interrogation, Castillo Villarreal confessed to approximately 12 murders, though prosecutors believe he may be linked to up to 20 killings. ​

On December 5, 2017, Castillo Villarreal was convicted and sentenced to 120 years in prison for his crimes. ​