Four months after 43 Mexican college students disappeared under suspicious circumstances, Mexican Attorney General Jesus Murillo Karam said on Tuesday that there is "legal certainty" that the teachers-in-training were murdered.

To date, 99 suspects have been detained with more at large, with CNN reporting that at a news conference in Mexico City on Tuesday, Karam said the students, who were ambushed by armed men on September 26, 2014, in Southern Mexico, were ultimately "abducted, killed, burned and thrown into the San Juan River" in a mass grave.

With "hundreds" of testimonies, pieces of evidence and 39 confessions in hand, the announcement appeared to put an end to the mystery around the case. After a number of theories were floated as to why the violent murders took place, Tomás Zerón de Lucio, head of Mexico's Criminal Investigations Agency, said in the end it appeared to be a case of mistaken identity.

Reacting to earlier reports that a local drug gang had ambushed the students at the behest of the mayor of the town of Iguala to avoid having them disrupt an event featuring his wife, de Lucio said the gang executed the male students because they mistakenly thought the men belonged to a rival drug gang operating in the area.

Former Iguala Mayor Jose Luis Abarca was earlier charged in the case and is awaiting trial after authorities claim that the students were captured by the Iguala police and turned over to the gang under Abarca's orders. Abarca's wife, Maria de los Angeles Pineda, has also been charged in the case.

This video (in Spanish) is the official reconstruction of what authorities believe happened.

Following months of protests over the lack of information about the students, supporters and victims' families held their own press conference on Tuesday in which they said they did not believe authorities, intimating that the Mexican military may have been involved in the plot.

The 43 men in their late teens and early twenties all attended a rural, left-wing teachers college that was known for taking anti-government stances. Karam emphatically denied that the military were involved in the incident.

According to CNN, friends and family of the 43 remain skeptical because so far only the remains of one student have been positively identified because the head of the Criminal Investigations Agency said the bodies were so badly burned that it was impossible to extract accurate DNA samples.

"I'm convinced that we should not remain trapped in this instant, this moment in Mexico's history, of sorrow, of tragedy and pain. We just can't dwell here," Mexican president Enrique Peña Nieto said on Tuesday.