Parents of the students see the resignation of Tomás Zerón as an empty gesture since he's being rewarded with another high-level government job.
Edgar Valdez Villareal became a somewhat larger-than-life figure after his arrest in 2010 when he smirked before news cameras and boasted that a movie would be made about his life in the drug world.
Despite the damning report by an independent panel, a government official defended the original investigation this week. President Enrique Peña Nieto said he would meet parents of the missing as the one-year mark approaches.
Mexico's chief criminal investigator said hundreds of smaller splinter cells continue to affect millions of Mexicans across the country. The statements were the most frank assessment made in years about Mexico's cartels.
Four months after the Ayotzinapa Normal School students were "disappeared," authorities offered no conclusive proof all 43 young men were incinerated at a dump, but also asked the public to move on.
Cartel members interrogated by authorities claim dozens of people — more than authorities admit — were attacked and killed because the cartel believed a rival gang was attempting to enter Iguala.