Some students highjacked several buses to go from one small town in Guerrero to another and several buses were shot at by local police, federal police and the army. It was more of an planned execution than an arrest from the very beginning as the arresting officers didn't give give the unarmed students a chance to surrender to them before opening fire and killing some of them. The ones who were arrested were beaten with rifle butts and some were murdered in the street. Some students fled and got on other buses but the authorities placed roadblocks around the town and wouldn't let anyone in or out. The whole town seemed to be complicit in the massacre to an extent as shopkeepers refused to serve the students food and drink, taxi drivers refused to pick them up and when they got to the hospital they were insulted and refused treatment, only for the army to come there and shoot some students dead and arrest some others. One local did help shelter some students in his house though.
Two buses with a total of 43 students in them were then stopped by the army and the students were arrested, never to be seen again. Some DNA from some students was then found by testing charred bones found in a nearby rubbish tip but most of the remains were too damaged to be tested for DNA. Despite this, most of the students are still unaccounted for, their DNA has not been found and no credible explanation has been given for what happened to them.
There are many flaws in the official story, the main one being that the alleged fire at the tip would have to use an incredible amount of wood or tyres to burn the students bodies as thoroughly as it did which would mean it would have been burning for days and would have been seen for miles around but we are expected to believe this fire passed unnoticed by the implausibly unobservant locals. Another problem is that there's a completely in burnt tree stump in the middle of the area where the conflagration was apparently located. The local military base had an incinerator and it seems far more likely that the students were murdered there and there remains dumped at the tip. Another flaw is that the police were only able to get local drug dealers to confess to the murders through extreme torture such as the electrocution of suspects' genitals and their confessions contradicted each other.
The official story is that the mayor, his wife and the military were corrupt and used a bus to smuggle millions of pounds of heroin - the students were murdered to cover this up. Perhaps it was used for this purpose but why murder the students when there's no evidence that they knew that any heroin was there? Why not just arrest them and move the heroin elsewhere or keep using the bus for smuggling purposes if the drugs were undetected? I wish this programme went into a bit more detail about this issue and explained why students would be so routinely high jacking buses in the first place though, so this excellent but not perfect series gets a 9 out of 10.