MONTERREY, Mexico (AP) -- Two police chiefs were shot and killed within hours of each other in a violence-plagued region near the United States where drug smugglers have been battling for control of key routes across the border. It wasn't immediately clear if the killings Monday were related, but authorities say violence has spiked in Mexico's northeast since the 2003 arrest of the area's top reputed drug dealer set off the turf war. Hector Ayala, chief of police in the wealthy town of San Pedro Garza Garcia outside Monterrey, was killed Monday when a car overtook his vehicle and opened...