(NewsNation) — The Mexican border town where the violent kidnapping of four Americans turned fatal last week has a dark history, dating back to 1989 when drug smuggling cult members abducted and murdered a University of Texas college student.

Mark Kilroy, a 21-year-old pre-med student, was last seen on a crowded street in Matamoros, Mexico, on the evening of March 14, 1989. Kilroy and his friends had been enjoying spring break, bar hopping in the border town when the group got separated.

Less than a month after his disappearance, authorities discovered Kilroy’s body, along with 11 others, buried on a ranch 20 miles outside of town.

Kilroy’s body had been brutally mutilated and dismembered. There were signs of human torture throughout the property.

Officials found candles and kettles full of body parts and animal bones, which were later determined to be the result of ritual sacrifices.

It was the work of a local satanic drug cult that had been importing about 1,000 pounds of marijuana a month into the United States.

The group’s alleged ringleader, Adolfo de Jesus Constanzo, had introduced “a sort of black magic” to the area, Oran Neck, then-U.S. Customs chief agent in Brownsville, Texas, said at the time.

Members of the drug gang would randomly select victims to sacrifice because they believed doing so put a “magic shield” around them that would protect the group from harm.

Authorities determined some of the cult’s victims had been shot in the head while others appeared to have been killed with machetes and sledgehammers.

Officials said group members made necklaces out of their victims’ vertebrae, unnerving even the most experienced investigators, who described the scene at Rancho Santa Elena as a “human slaughterhouse.”

At least 15 people were killed in ritual slayings at the property, although more are suspected to have died there. In 1994, five members of the cult were sentenced to more than 60 years in prison for the deaths of Mark Kilroy and 12 others.

Less than two months after Kilroy disappeared, Constanzo, who had fled the area, ordered one of his followers to shoot him before law enforcement closed in.

Today, the U.S. State Department has issued its highest “Do Not Travel” warning for the northern Mexican state of Tamaulipas, where Matamoros is located, due to “crime and kidnapping.”