WASHINGTON -- State and federal law enforcement officers appeared before senators Wednesday to paint a horrific picture of life on the Southwest border, telling of violent assaults, running gunbattles, brazen cross-border incursions and threatened contract killings of U.S. officers. The hearing, co-chaired by Sens. John Cornyn, R-Texas, and Jon Kyl, R-Ariz., prompted calls for a border crackdown to combat what Kyl described as "bad, nasty, dangerous people." U.S. Border Patrol Chief David Aguilar showed slides of battered agents, telling senators that his officers increasingly fall victim to attacks by assailants firing weapons, hurling rocks or pursuing the agents with vehicles....