It has been described as one of the most horrific chapters in Mexico's drug war.
According to prosecutors, it was members of the now-split drug cartel Los Zetas who began forcing young men, on their way to the Mexican border town of Reynosa, to get off the buses they were traveling on – due to suspicions that a rival cartel was using the buses to send reinforcements to border towns they controlled.
The passengers were interrogated by the cartel and some were offered the chance to live and join the gang – if they proved their worth by fighting other innocent passengers with hammers.
The tragedy was first discovered in 2011 when 48 unmarked graves containing nearly 200 bodies were found in the state of Tamaulipas. Many had had their skulls crushed by hammers, while others were Central American migrants who were killed by Los Zetas during the same period after they refused to join the gang. Some hammers were also found in the graves.
The eleven cartel members were arrested between 2015 and 2017. After trials that have lasted for several years, they are now being sentenced to 50-year prison terms.