Torreon, Mexico - Two teenage brothers armed with knives and fireworks killed a female assistant principal and injured three other people in an attack at a Mexican school on Thursday.
While several parts of Mexico live under the threat of brutal cartel violence, school shootings or stabbings are rare.
Authorities said the two 18-year-old alleged attackers previously attended the school in the town of Torreon in Coahuila state, which borders the US.
State prosecutor Federico Fernandez told reporters the siblings entered the facility and attacked staff first before targeting students.
"The motive they indicated preliminarily was a personal vendetta against the school," Fernandez said.
Mexico's El Universal newspaper reported that the pair had threatened, on their arrival, to attack women.
Fernandez said at least one of the injured was in critical condition. He did not give the ages or gender of those who were wounded in the attack.
The most recent deadly school attack in Mexico took place in March, when two teachers at a private school in western Michoacan state were shot dead, allegedly by a 15-year-old student.
A social media post before that attack showed the suspect posing with a rifle and displaying messages linked to the "incel" movement, short for "involuntary celibate," an online subculture that promotes hatred of women.