TIJUANA, Mexico - Rosalba Padilla thought the first shots were nothing but construction in her quiet, upper-class Tijuana neighborhood. It wasn't until she looked out her window and saw a sea of police that she realized the noise was gunfire. Down the street, at the Preschool of Happiness, director Gloria Rico activated the school's alarm, prompting police to rush into the building, their guns drawn. Rico said the children were terrified by the chaos. "Some were crying, one vomited and another wet his pants," she said Friday, adding that the police quickly put away their weapons and started evacuating the...