 The attorney general's office would not reveal which of the two warring cartels—the Gulf Cartel or the H. Cartel—in Ciudad Obregón wrote the note.Mexico has become one of the most dangerous places for journalists in the world, but observers have noticed a sharp rise in the violence against journalists heading into the 2012 presidential elections.In the month before Ávila's murder, six other journalists have been killed in drug-related violence.