Mexico City (CNN) Emiliano Navarrete says it was the worst night of his life: Friday, September 26, 2014. Navarrete was home with his wife when he suddenly received a phone call. It was his son José Ángel, who sounded terrified on the other side of the line.

"I asked him what was happening," Navarrete said. "Father," his son said, "we're being attacked by the police. They already shot my friend. He's lying on the floor. He was shot in the head."

Navarrete said he could hear the commotion his son was describing on his cell phone: young men screaming in terror. "Then I told him, 'You know what, son? Try to hide or escape. Be on the alert. Escape if you can so that they don't harm you. Take very good care of yourself.'"

That was the last thing he was able to tell his son. The phone went silent. Communication was lost.

Navarrete didn't know it at the time, but it was just the beginning of a case that would not only deeply affect his family, but also send shock waves across the Mexican justice system and the country's security forces. It has been one year. The ensuing scandal continues to shake the administration of President Enrique Peña Nieto.

Survivor recounts panic, hiding for hours, days

Protesters march near the Angel of Independence monument in Mexico City on Saturday, the first anniversary of the disappearance of 43 college students in Guerrero state.

José Ángel Navarrete, who was 18 at the time of his disappearance, was part of a group of about 100 students traveling in several buses in the state of Guerrero on the night of September 26. The young men were students at the Raúl Isidro Burgos Teachers' College in the small town of Ayotzinapa. The educational institution was created to train teachers who would go to some of Mexico's most isolated and impoverished communities.

But at Burgos, students also learned their politics. Most of the students went to the rural college because their parents, mainly impoverished peasants, couldn't afford to send them elsewhere. They came from families that felt abandoned and marginalized by the Mexican government.

Murals honoring Marxist guerrilla fighter Ernesto "Che" Guevara are everywhere at Burgos, as well as other leftist icons such as Mexican guerrilla fighter and rural teacher Lucio Cabañas, who was killed by Mexican soldiers in 1974.

In the school's courtyard is a monument honoring the memory of two students who died in a clash with police in December 2011 as the officers were trying to reopen the highway connecting Mexico City and Acapulco, which was blocked by a group of students.

The night they were attacked, the students were traveling in buses to the nearby city of Iguala to raise money for their activities, according to Neri de la Cruz, one of those who survived the attack.

"When I heard the shots, the first thing I did was look back to make sure my fellow students were doing OK. I saw when one of them was shot in the head. He turned his face and fell to the ground. At that moment, we panicked," de la Cruz said.

What happened next is hard to ascertain. De la Cruz is among the survivors who say that they were shot at by police officers, but they ran away and had to stay in hiding for the next hours and days. The official version from Mexican authorities is that the students were indeed attacked by local police officers from the cities of Iguala and Cocula who then handed the students over to a local drug gang known as United Warriors (Guerreros Unidos).

Then-Mexican Attorney General Jesús Murillo Karam said at a January 27 news conference that there was "legal certainty" that the 43 missing college students were murdered. He said 99 suspects had been detained so far. Evidence, Murillo Karam said, included hundreds of testimonies, confessions and pieces of evidence.

"These and other elements we found during the investigation allowed us to carry out an analysis about the logical causes and, without a doubt, we can conclude that the students at the teachers' college were abducted, killed, burned and thrown into the San Juan River, in that order," Murillo Karam said.

The attorney general was dismissed exactly one month later.

Casting doubt on the official story

Posters of the missing line the Angel of Independence monument in Mexico City.

The parents rejected the Mexican government's official version that the students were burned to ashes in a landfill, insisting there was no evidence. Several parents made serious accusations suggesting there was a cover-up. Eight months later, an independent report by the Inter-American Human Rights Commission (IAHRC) would also cast doubt on the government's version.

Earlier this month, a group of experts commissioned by the IAHRC discredited the Mexican government's official version. After a six-month investigation, the experts issued a report concluding there's no evidence to support the hypothesis that 43 bodies were cremated in the local landfill last September 27.

"Flames would've reached seven meters and the smoke column would have risen 300 meters," the report said, suggesting it would've been seen by several surrounding communities, which wasn't the case.

"The flame, the seven-meter flame, would've had to tilt toward the dump, igniting all of the plastic that's still there. It is a rather dry dump and, therefore, this would've caused a wildfire that would've burned all of that area," commission investigator Francisco Cox said.

Felipe de la Cruz, father of survivor Neri de la Cruz and spokesman for the groups of parents, says the new report proves Mexican officials had been lying all along.

"The play staged by the Mexican government has collapsed. The so-called 'historic truth' of [former Attorney General Murillo Karam] fell to the ground and became the 'historic lie,'" de la Cruz said.

Just hours after the new report was released, current Attorney General Arely Gómez González said Mexico would launch a new investigation at the landfill site.

President Enrique Peña Nieto backtracked, saying his government is still on the case.

"The case, as we have been saying, remains open. The investigation continues. It will be the judicial branch that will determine when it will close and give final conclusions. The search for the missing students remains. It's currently being done in an individualized way, as the parents have requested," Peña Nieto said.

Erika Guevara-Rosas, Americas Director at Amnesty International, says the Mexican government's insistence in proving its original theory distracted investigators from other lines of investigation. She says the government should not rule out a conspiracy involving the military or police forces.

"The Ayotzinapa tragedy is one of the worst human rights tragedies in Mexico's recent history. It has exposed how anyone can be forcibly disappeared into thin air in the country with those in power focused on covering up the traces. Unless President Peña Nieto takes real action now he will continue to be seen around the world as an enabler of horrors," Guevara-Rosas said.

Now, a year after his son's disappearance, Emiliano Navarrete still chokes up almost every time he talks about his son. CNN caught up with him at Mexico City's main square or Zócalo on Friday, as he was at the very end of a 43-hour fast staged by the students' parents, one hour for each missing child.

Navarrete is 40 years old. He hasn't gone back to his work in construction since his son went missing. He and his family survive on donations from people sympathetic to the parents of the missing.

Navarrete says he will continue to assume his son is alive until it is scientifically proven otherwise, a feeling he shares with the rest of the parents.

"Believe me," Navarrete says, "I will bring him back. He will come back one day."