At 8am one Wednesday, lawyer Marcelo Fernando Martinez Gonzales entered the office of pre-school headmistress Carla Maria Jimenez Bolanos at the private, bilingual Winston Spencer Churchill school in Mexico City. He then shot the 36-year-old teacher dead in front of horrified pupils and parents.
When apprehended, the 50-year-old lawyer said: "The gun went off." He claimed that his daughter had been sexually assaulted at the school. Forensics revealed that he was a habitual cocaine user and that he was high at the time of the murder.
In a country where the gunning down of 12 people in a bar doesn't make the front page, the Churchill school incident was just another news item. Mexico's schools are, after all, the most dangerous in the world.
This was shown in a study published last month by the Organisation for Economic Co-operation and Development, which rated Mexico's secondaries the most violent of the 23 countries surveyed.
Research for the OECD's Teaching And Learning International Survey (Talis) was carried out in 2007 and questioned 90,000 teachers worldwide. The heads of 192 public and private secondaries in Mexico said there was a climate of violence in their schools: 61 per cent reported intimidation and verbal abuse among students; 57 per cent physical aggression; 56 per cent robbery or theft; 51 per cent use or possession of drugs or alcohol; 47 per cent intimidation or verbal abuse of staff.
No other country in the survey was close to Mexico in levels of violence.
The study's results were presented in Mexico last month by OECD secretary general Angel Gurria. "While this survey shows that the challenges are tough, it also suggests that many teachers and school principals are ready to address them," he said.
On top of the violence, Mexico's schools also had the greatest problem with teacher lateness, absence and poor training. In many states, teachers hold other jobs and can be absent from classes for three-quarters of the time - understandable perhaps, given the hazards they face.
Take the case of Roberto Esquivel, a maths teacher at the Humberto Munoz Zazueta Secondary School No 5 in Southern Baja California, who fell ill after drinking a cup of coffee. Esquivel habitually asked his pupils to bring him coffee, and two girls in his class saw this as their chance to exact revenge on him for failing them in an exam. They slipped three powerful sedative pills in his mug. "The teacher was like a zombie," said one pupil. "I watched him trying to drive his car when he crashed it."