On​ the night of 26 September 2014, in the town of Iguala in the Mexican state of Guerrero, local police opened fire at several buses – some full of students, one carrying football players coming home from a match. Six people were killed. By midnight, 43 more students had disappeared, or, rather, had been forcibly disappeared. That’s where the story fades to grey. The Mexican government at first claimed that the police had handed the students over to a local narcotrafficking outfit, which murdered them, incinerated their bodies and buried the bones in a mass grave. But the official story kept changing, and it was plain a cover-up was underway. As the case of the missing students became international news, parents and activists went looking. They found first one mass grave, then another and another and another. Not their children’s. Other bones. It turns out that Mexico is riddled with secret mass graves (fosas clandestinas).

Forced disappearances call to mind the Cold War era dictatorships in South and Central America, but Mexico had its own dirty war. When the teenagers disappeared, they had been preparing to commemorate the most infamous episode in that war, the 1968 Tlatelolco Massacre. Ten days before the Olympics opened in Mexico City, at the president’s orders, soldiers in plain clothes and rooftop snipers ambushed a student protest, killing at least three hundred. The government denied that a massacre had taken place, calling it merely a ‘confrontation’. Soldiers bundled away the bodies so that an accurate count of the dead has never been possible and families had no remains to bury. Each year on 2 October a memorial service is held in the plaza in the Tlatelolco area of Mexico City where the massacre took place. This is where the students attacked in Iguala planned to go, and this was why they commandeered the buses, boarding with their faces covered and forcing the drivers to take them where they asked. The practice is known as ‘kidnapping’ buses, and was of a piece with the ethos of the school the teenagers attended.

The Raúl Isidro Burgos Rural Teachers College is known to everyone as Ayotzinapa, the name of the village where it is located. Ayotzinapa was one of a network of teacher training colleges founded in the 1920s, during the most radical period of the Mexican Revolution. The revolution led to two lasting changes: more land and rights for peasants (campesinos), and the emergence of a political party that brooked no opposition. Its name has always struck me as a contradiction, almost but not quite a joke: the Partido Revolucionario Institucional (PRI), the Institutional Revolutionary Party. It ruled, uninterrupted, from 1929 to 2000 by stealing elections, buying the press and stubbing out dissent. Mario Vargas Llosa called the Mexican system the perfect dictatorship, since it was dressed up in enough elections to pass as a democracy. The PRI of this period is sometimes described by historians as a dictablanda, a soft dictatorship, punning on dictadura. The PRI, a nominally left-wing party, resorted to dirty war tactics – forced disappearances, infiltration of socialist and communist groups – to maintain power at national, regional and local levels. In states like Guerrero the soft dictatorship was not so soft. Local elites had their enemies flown out over the Pacific and then pushed out of helicopters.

The radical strain of the revolution that produced the rural teacher training colleges quickly faded, and for decades the students have had a contentious relationship with the authorities. Ayotzinapa’s walls are decorated with murals of Lenin, Che Guevara and Subcomandante Marcos – the leader of the 1994 Zapatista uprising. The colleges maintain their original teaching style, a hands-on education à la Montessori mixed with political consciousness-raising. Room, board and tuition are free, but the students lead a gruelling life. They clear weeds with machetes, feed pigs and hens, and grow corn, beans, vegetables and flowers, which they sell at market and share with the locals they call ‘aunt’ and ‘uncle’. Students are from poor, often indigenous families. One student cited by John Gibler in his valuable oral history of the massacre, said that ‘we don’t have any other options for study or pursuing a career, my small town is a bit more fucked-over than other places. I decided to come to this school, to study, to be someone.’ Graduates become teachers in the countryside, one of the few avenues of social mobility that doesn’t involve joining a gang or hiring a coyote – someone who smuggles people – and crossing to the United States.

The PRI has long seen the teacher training colleges as seedbeds of political dissent, which spreads to the rural schoolhouses where graduates teach. Rural teachers helped start the revolution, and the PRI has not been anxious to see another one. There were once 36 similar teacher training colleges across Mexico, but following the student unrest of 1968 President Gustavo Díaz Ordaz had 18 of them closed down. The remaining colleges operate on a shoestring budget. Students defend the practice of commandeering buses by pointing out that the government has starved the colleges of resources, requiring them, for example, to attend ‘observation’ courses at other schools but not providing funds for transportation. When the students kidnapped buses, it was to enable them to travel to other schools or to anti-government protests. The Ayotzinapa students suspected, rightly, that they were under government surveillance and used nicknames: Cochiloco (‘Crazy Pig’), Shaggy, Pepe, Bobby, Dormilón (‘Sleepyhead’), Pato (‘Duck’), Pinky. Some didn’t know their fellow students’ real names, adding to the confusion on the night of the disappearances. While the practice of commandeering buses was seen locally as an annoyance at worst, it would be exploited by mass media on the government payroll to portray the teenagers as thugs or even narcos.

During the Cold War, global conflict provided a context and excuse for local score-settling and suppression of enemies in Latin America. Government officials could torture or disappear anyone: all they needed to do was to call them a communist. Now the drug war provides similar cover. In Mexico in the 1970s some left-wing guerrilla groups were indeed plotting a revolution. But the government vastly overestimated their reach and power in order to justify repression. Two of Mexico’s best-known guerrilla fighters were teachers who graduated from Ayotzinapa and were later hunted down by the army. Now, anyone whom agents of the Mexican government wish to arrest, torture – even murder execution-style – can be disappeared if they are said to be a narco. Sometimes they are. Often they are not.

Many Mexicans assume that the cartels work hand in hand with the government, at local, state and even federal level. In 2006, by which time the drug war’s frontline had moved from Colombia to Mexico, the newly elected president, Felipe Calderón, announced that he would wipe out the cartels. Two years later, the US coughed up $1.5 billion to help with the effort. When I moved to Mexico in 2009, a popular topic of conversation was whether Calderón really wanted to eradicate the gangs or whether he was in cahoots with one cartel and using US money to target its rivals. When a plane crash-landed in the middle of Mexico City, killing José Luis Santiago Vasconcelos and Juan Camilo Mouriño – a former prosecutor known for fighting the cartels and the interior minister – the rumour mill went wild. It was an accident, the government said, but many people believed – without evidence – that the cartels had shot the plane down, or that it was all a government plot to rein in over-enthusiastic investigation of narcotrafficking that might lead back to high places.

That the Mexican state apparatus is infiltrated by narcos is both rumour and fact. I remember hearing an anthropologist asked when it was and was not appropriate to use the word ‘narcostate’: ‘Well, on one research trip I interviewed some narcotraffickers,’ she said. ‘And the next trip I interviewed one of the same informants, but now he was the mayor.’ It is harder to cite proof at the federal level, though a witness at the recent trial of the drug lord El Chapo alleged that Enrique Peña Nieto, the PRI president at the time of Ayotzinapa, accepted a $100 million bribe from the Sinaloa cartel. We don’t know exactly who is involved with what, or when. Who brought down the plane, if anyone? Who disappeared the students? Given the predation, corruption and bad faith of the state at all levels, many Mexicans don’t even bother calling the police when they are robbed, never mind when they witness a crime. ¿Para qué? The police will make it worse. And they might tell the criminals.

There had been other massacres, and many other disappearances, before the students went missing. It is estimated that 130,000 people have been killed in the Mexican drug war, and 27,000 people disappeared. But after the Ayotzinapa massacre something snapped. The next day, people were out on the streets in Mexico City, in Guerrero, all over the country, chanting: ‘Fue el estado! Fue el estado!’ It was the state.

There are​ many, many different versions of what happened that night in Guerrero, the least reliable of which is the official story. What we know is that a group of students left the college in Ayotzinapa in the afternoon to commandeer buses. They were in a festive mood. ‘We were messing around like always, you see how we are, talking, fucking around, talking about girls,’ one of the students told Gibler. ‘The freshmen were all making jokes.’ The students, travelling in two buses they had previously secured, wanted to ‘kidnap’ more from Iguala’s bus station. When they pulled into town it was already dark, and raining. Local police put up roadblocks to stop them leaving with the new buses, and intercepted them, along with another bus painted in similar colours, which was carrying a football team home from a game. Suddenly, police started shooting into the buses, shattering the windows. ‘You’re dead, you fuckers,’ one student heard them shout. The police forced the students and football players out of the buses, and some ran into the nearby cornfields. Those who got away saw their schoolmates being forced into patrol cars. One student had a full-blown panic attack, and was convulsing. ‘They dragged him along by one hand and one foot. When they put him in the back of the squad truck, they tossed him like an animal, like he was some sack of flour,’ another student said.

The students had seen confrontations with the police before, but not like this. One said that standoffs usually ended peacefully when the police saw that the students weren’t armed. The police would say: ‘“Young men, you can’t grab vehicles like that, you have to come to an agreement with the bus companies and blah, blah, blah,” stuff like that. But at that moment, the police didn’t act like that. We said, “We’re students, we’re unarmed,” but the police didn’t give a shit.’

Days later, the government announced that the case was closed. The official story was that the attacks had been ordered by Iguala’s mayor and his wife, members of the opposition PRD (Party of the Democratic Revolution). The mayor’s term was coming to a close, and that night a public meeting had been held at which his wife launched her own campaign to succeed him. According to this account, the students had planned to interrupt or demonstrate at the event, and the mayor and his wife had given orders for them to be intercepted and handed over to a local drug gang with which they were supposed to have ties. Radio, television and the newspapers enthusiastically pumped out this story, painting the mayor’s wife as a Lady Macbeth, the ‘First Lady of Murder’. It was her misfortune that she was good-looking and ambitious.

The only part of this story that was true was that the mayor’s wife’s two brothers had worked for the Beltrán-Leyva cartel. Several leaders of the local gang, Guerreros Unidos, had been gunmen for the same cartel. The mayor’s wife always maintained that her brothers had died long before her husband became mayor, and that she and her husband had no connections to trafficking. But even if a connection had been proved – and it was not – the story made no sense. Students who survived the attack said they hadn’t known that a campaign launch was to take place, and in any case, by the time of the attack, the launch was already over. The mayor and his family were sitting down to tacos at a stand in another part of town.

It was​ the state, but not that branch of the state. Who, then, ordered the attack? And why? One of Mexico’s best-known investigative reporters, Anabel Hernández, believes the plot goes all the way to the top. Two months after the massacre, she published an account in one of the country’s few reliably independent news outlets, Proceso, based on interviews with survivors, suggesting that the federal police and the army had been present on the streets of Iguala that night. (Students told Gibler the same thing: local police shot at them, but they saw state and federal police at the scene.) Hernández explained that there is a command and control centre in Iguala called C-4 which co-ordinates military and police intelligence: it was impossible for the federal government not to be aware of events as they unfolded.

Hernández has now published a book, A Massacre in Mexico, in which she makes a bigger claim: the attack was ordered by the governor of Guerrero, Angel Aguirre Rivero, and, she suggests, by the president himself, Enrique Peña Nieto of the PRI. ‘For the government of Guerrero … as well as for the federal government’, the students had ‘turned from a perpetual headache into a public enemy – a target they believed they could rid themselves of with impunity’. Over the five days leading up to the attack, she claims, Aguirre Rivero and Peña Nieto ‘were closely co-ordinating and preparing to quickly respond to and halt the students’ commandeering of buses’.

But Hernández has a source problem. She has sources, of course – but she is not always as clear as she might be about who or what they are, even bearing in mind her duty to protect their identities. The book has no footnotes or endnotes. ‘During my investigation’ is a phrase that recurs, often without further detail. I am loath to write this, sitting as I am in New York City, and knowing that Hernández took very real risks to produce this book. But in order to persuade the reader that the attack was actually ordered at the very highest levels of government, she would have had to give some indication as to where her information comes from. She makes much of a 2012 document that lists Ayotzinapa as a national security concern for the incoming administration of Peña Nieto, but this document alone hardly proves intent. The question of who ordered the attack and why remains unsolved. Gibler’s oral history, which captures the chaos and confusion of the night, is a better guide to the actual attack – but he makes no claim to have solved the mystery.

What Hernández’s book lacks in persuasiveness about the events leading up to 26 September is more than compensated for by her detailed coverage of the government’s horrifying and often clumsy attempt at a cover-up. In January 2015 a new claim – that the 43 students had been temporarily held by the Iguala municipal police, who then turned them over to the Guerreros Unidos gang, who incinerated their bodies at a rubbish dump near the town of Cocula – was put forward by Jesús Murillo Karam, the then attorney general. Murillo Karam described this version of events as the ‘historical truth’– a phrase that has become as infamous in Mexico as Kellyanne Conway’s ‘alternative facts’ in the US. According to the ‘historical truth’, which the government claimed had been derived from confessions by police and gang members, the killers had disposed of the burned remains in various places, including a nearby river. The government produced 19 charred bone fragments, which were sent to an Austrian laboratory that produced one positive DNA match: Alexander Mora Venancio, who was 19 years old.

There was one problem. The families of the disappeared had called in the Argentine Forensic Anthropology Team, internationally respected for their investigations into dirty war crimes. The organisation found that Mora Venancio’s bone was different from the other charred remains. It was a larger fragment and not as severely burned. What’s more, the ‘chain of custody’ of the evidence couldn’t be vouched for – the implication being that the government had planted the evidence at the river. Meanwhile, Hernández and other independent reporters were publishing stories suggesting that the ‘historical truth’ was based on confessions extracted through torture. The parts of Hernández’s book that detail this torture, including repeated rapes, are based on interviews with some of the suspects the police rounded up and their families – here her sources are clear and convincing. Accounts of the attorney general casually sending orders to destroy the lives of people he must have known had nothing to do with the crime make for excruciating reading. Even if the planning of the attack didn’t go all the way up, the cover-up certainly did.

Uproar over the forensic science and forced confessions spilled over into massive protests that looked, for a time, like they might bring down the government. Eventually, Peña Nieto agreed to permit the Inter-American Commission on Human Rights to appoint a group of five legal experts from different countries to investigate the case. Their first report landed like a bomb on 6 September 2015. It confirmed what the survivors had always maintained: that federal police and army officials were present that night – a clear contradiction of the government’s version of events. The local police had committed the massacre, but the federal police had acted aggressively and failed to help the wounded; from the moment the first bus left Ayotzinapa in the afternoon, the army had monitored the students’ movements from the Iguala command and control centre. The Interdisciplinary Group of Independent Experts (GIEI) also found that, despite rumours in the press, there was no evidence that any of the students had ties to drug-trafficking gangs. The confessions supporting the ‘historical truth’ had been extracted through extensively documented torture of 80 per cent of the suspects held in the case, confirming Hernández’s account. One fire forensics expert found that it was ‘scientifically impossible’ for 43 human bodies to have been incinerated in the Cocula dump in the way claimed by the attorney general’s office. The charred bone found in the river wasn’t evidence of anything other than a cover-up. The ‘historical truth’ was a lie.

The report did not resolve who exactly was responsible for the disappearance of the students, or where they were taken. But it recommended that the federal police and army be investigated as well as the local police. At this point, as a way of responding to the torture allegations, the government opened a series of investigations into its own investigators, creating a peculiarly Mexican hall of mirrors. They refused, however, to allow the independent experts to complete a second investigation, denying them interviews with military officials and federal police and engaging in what the GIEI described as a campaign of harassment and intimidation.

The team left Mexico early in 2016. But on 16 April that year they published another report, putting forward new evidence to support what they called the ‘theory of the fifth bus’. The students said that they travelled to Iguala on two buses, and managed to commandeer three more there. The attacks occurred when they had five buses, plus the bus full of footballers: six buses. But one of the three newly commandeered buses was not taken into account in the original investigation. It was stopped by federal police as it left Iguala and impounded. The federal police allowed the students to escape – unlike the local police, they didn’t shoot. The GIEI report noted a criminal complaint filed with the US attorney’s office in Illinois in 2014 alleging that members of Guerreros Unidos smuggled heroin and cocaine on commercial buses just like the ones taken by the students. Was the attack a desperate attempt to recover a bus carrying valuable cargo on the part of a drug gang and the authorities on its payroll? In her book, which came out in Spanish before the second expert report, Hernández provided a similar scenario. ‘A high-level drug trafficker with much business in Guerrero’ whom she interviewed told her that the students were unknowingly travelling in two buses carrying a concealed stash of at least $2 million of heroin. The source said he called the army to help him get the heroin back. If the local police were colluding with the gang, it would explain why they opened fire to get the bus back. Or the narcostate might extend higher up, to the governor’s office or further. Just because Hernández doesn’t present sufficient evidence to support her account of who planned the attack doesn’t mean she’s wrong.

A London-based research agency called Forensic Architecture also took on the case, in collaboration with Mexican human rights groups and the Argentine forensic scientists. Forensic Architecture compiled security videos, witness testimonies, phone logs, photographs and news reports into an enormous database that mapped the massacre over time on Iguala’s streets. The group converted its database into an interactive map, which includes three-dimensional reconstructions of the attacks, and shows how the Mexican government mishandled and planted evidence as part of the cover-up. The disappeared students appear as featureless little red dolls, face down in the back of police trucks. As you toggle around this map, what Forensic Architecture calls the ‘high level of co-ordination and collusion’ becomes clear.

The interactive map resembles a much more sophisticated cartographic version of a chronology that I tried and failed to sketch out while reading Gibler, Hernández and the independent experts’ reports. Forensic Architecture acknowledges that the ‘sheer amount of information produced by the case’ – the narratives and counter-narratives – means that some of the five thousand data points used for their reconstruction may be inaccurate or contested. Still, their project makes the scale and confusion of the events of the night clearer than a written text, which is by necessity linear, can do. Forensic Architecture are continuing to update the database with new or clarified data. It is intended as both a visualisation and a forensic tool for the ongoing investigations.

Both​ Gibler and Hernández’s books are inspired by Elena Poniatowska’s famous account of the 1968 Tlatelolco massacre, a collage of oral histories, photographs, protest chants and poems by Octavio Paz and Rosario Castellanos that gave the lie to the government’s version of events. The book was called La Noche de Tlatelolco in Spanish and Massacre in Mexico in English. (Hernández’s book is called La Verdadera Noche de Iguala in Spanish.) Poniatowska – who on the fiftieth anniversary of Tlatelolco told the New York Times that ‘it is very easy to produce cadavers in Mexico: it is very easy to die here’ – is still the writer to turn to in order to understand the meaning of what happened to the students of Ayotzinapa. Sergio Aguayo, a leading activist and intellectual, made the argument in the subtitle of his book, De Tlatelolco a Ayotzinapa: Las Violencias del Estado (‘From Tlatelolco to Ayotzinapa: The Violences of the State’). A state has a legitimate monopoly on the use of force in order to guarantee the security of its citizens, but when it turns its guns on its own citizens it is no longer legitimate. For Aguayo, the Mexican state gave up legitimacy a long time ago. He has investigated other massacres and disappearances, and concludes that ‘the state neither protects us against criminals, nor does it care for us as victims. We are helpless.’

New president, same state. The horror over Ayotzinapa, and the way that the missing 43 came to stand in for all those who disappeared during the drug war, helped get Andrés Manuel López Obrador, known to everyone as AMLO, elected last year. Since the democratic opening in 2000, AMLO is only the third president of Mexico to belong to a party other than the PRI. (His party, Movement for National Renewal, is known by its acronym, Morena, another name for Mexico’s religious icon Our Lady of Guadalupe.) His first presidential decree established a ‘truth commission’ to conduct a new investigation into Ayotzinapa, and he has promised to invite the independent experts back. Two days after he was sworn in, he invited the parents of the missing students to the National Palace and promised that ‘there will be no barriers, no obstacles to arriving at the truth.’ He also announced that he would open the archives of the national security intelligence service, to allow researchers to find out how those who opposed the PRI – including the leaders of the 1968 student movement – were put under surveillance and targeted. How the new Ayotzinapa investigation unfolds will be a litmus test for many Mexicans. If AMLO solves the case, he’s with us. If not, he’s just another politician. No matter what he does, some Mexicans will never trust their government again. Other bones remain in the ground.