On January 31, an armed commando unit pulled up to a house in a working-class neighborhood in Ciudad Juarez on the Mexican side of the border with the United States. Inside the house, 60 teenagers were celebrating a friend’s birthday. Wielding high-caliber weapons, the commandos opened fire on the kids, robbed the house, then drove away from the scene — amid human cries, the scent of gunpowder, and the total absence of law enforcement officials.


