After Monterrey saw piles of severed heads and corpses hanging from overpasses, it was hard to imagine a more gruesome attack in Mexico's industrial heartland. But the survivors pulled out of the city's burning Casino Royale described the truly hellish dimensions of the worst act of violence in the city in recent memory. The massacre illustrates how Mexico's drug cartels have steadily raised the stakes in trying to outbid one another as the most brutal player in the conflict. While their victims used to be limited to gangsters and police, now they are increasingly civilians, with catastrophic consequences.

CTV footage shows a gang of eight gunmen descending on the casino, located in an upper-middle-class neighborhood, on Thursday afternoon, Aug. 25, while about 150 croupiers and customers — mostly women — played bingo, roulette and slots. The scene quickly descended into psychosis and panic, as the crowd stampeded from the games into bathrooms, stairwells and a blocked emergency exit. They heard gunfire and explosions that they thought were grenades and saw men pour gasoline over the machines and set them alight. As the building burst into flames, most of the victims choked to death in trapped corners, while others burned as they tried to escape or were crushed by the stampede. When emergency crews finally smashed down the walls to rescue the survivors, corpses littered the game tables, stairwells and bathrooms. By Friday morning, police had counted 52 dead; dozens more were in hospitals.