One of Mexico’s most controversial mass killings where 43 students headed to a protest were kidnapped by police and cartel allies took a turn in recent days. New evidence indicates the order to kill and dispose of their remains came from drug lords in Chicago.

The mass killing took place in 2014 in Guerrero, when a group of students stole buses on their way to a protest. At the time, Mexico’s government claimed that 43 students had been kidnapped by police and turned over to cartel members to be killed and incinerated in a landfill near the town of Cocula. That version of events became known as the Historic Truth. Shortly after, questions arose about the validity of the story when forensic evidence was reviewed by international experts.

Last week, the case made headlines after Mexico’s Undersecretary for Human Rights Alejandro Encinas released a report claiming the massacre was a “crime of state” and officials at the highest levels attempted cover-ups. Days after the release of the report, authorities arrested the former Attorney General of Mexico, Jose Murillo Karam, for his role in creating the Historic Truth and torturing suspects.

New information detailed in Encinas’ report revealed that U.S. authorities had tapped phones and intercepted messages belonging to brothers José Ángel Casarrubias Salgado and Adan “El Tomate” Cassarrubias Salgado, living in Chicago. According to Milenio, those surveillance efforts led to the discovery that the kill order originated in Illinois.

The U.S. Government tapped the lines to investigate heroin smuggling schemes between Chicago and Guerrero. The two brothers, along with a third in Mexico (Sidronio Casarrubias Salgado), and other relatives were the leaders of Guerreros Unidos, a splinter of the Familia Michoacana Cartel.

The phone messages and conversations reportedly revealed the brothers’ beliefs that rivals had infiltrated the students and were using the buses to smuggle themselves into their territory.

The brothers relayed to their henchmen in Mexico to get rid of the evidence. According to Milenio, since there were too many students, a cartel lieutenant known as “El Chucky” had his men use machetes to dismember the bodies and place them into bags. El Chucky then had each cell of gunmen take bags and dispose of the remains.

Ildefonso Ortiz is an award-winning journalist with Breitbart Texas. He co-founded Breitbart Texas’ Cartel Chronicles project with Brandon Darby and senior Breitbart management. You can follow him on Twitter and on Facebook. He can be contacted at Iortiz@breitbart.com

Brandon Darby is the managing director and editor-in-chief of Breitbart Texas. He co-founded Breitbart Texas’ Cartel Chronicles project with Ildefonso Ortiz and senior Breitbart management. Follow him on Twitter and Facebook. He can be contacted at bdarby@breitbart.com.     

“C.P. Mireles” from Breitbart Texas Cartel Chronicles project contributed to this report.