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The chaotic drug violence in Mexico continues unabated. With more than 6,000 killed in the past few years, today we can add yet another victim: the country's national police chief, killed by gunmen outside his home in Mexico City yesterday.

Edgar Eusebio Millán Gómez, the public face of Mexico's offensive against drug cartels, became the highest-ranking law enforcement official to be killed since the launch of the effort 17 months ago. The assassination could give new confidence to drug cartels blamed for 6,000 killings in the past 2 1/2 years, and embolden other anti-government groups in this violence-plagued nation.

"This could have a snowball effect, even leading to the risk of ungovernability," Luís Astorga, a Mexico City-based sociologist and drug expert, said in an interview. "It indicates terrible things, a level of weakness in our institutions -- they can't even protect themselves."