On March 14, 1989, University of Texas at Austin student Mark James Kilroy was kidnapped in Matamoros, Tamaulipas, Mexico, while vacationing during spring break. He was taken by his abductors to a ranch where he was tortured and sodomized for hours before being murdered in a human sacrifice ritual. Kilroy was killed with a machete blow and then had his brain removed and boiled in a pot. His killers then inserted a wire through his spinal column, amputated his legs at the knees, and buried him at the ranch along with 14 other people who had been killed there before him. Adolfo Constanzo, the leader of the cult, told his followers that human sacrifice granted them immunity from law enforcement for their drug smuggling operations. The killing drew worldwide media attention and initiated an international police manhunt because of the unusual circumstances of the crime.

Matamoros, officially known as Heroica Matamoros, is a city in the northeastern Mexican state of Tamaulipas, and the municipal seat of the homonymous municipality. It is on the southern bank of the Rio Grande, directly across the border from Brownsville, Texas, United States. Matamoros is the second largest city in the state of Tamaulipas. As of 2016, Matamoros had a population of 520,367. In addition, the Matamoros–Brownsville Metropolitan Area has a population of 1,387,985, making it the 4th largest metropolitan area on the Mexico–US border. Matamoros is the 39th largest city in Mexico and anchors the second largest metropolitan area in Tamaulipas.