Tension is growing along the American border with Mexico after a U.S. border agent shot and killed a 15-year-old Mexican boy on Monday evening. The incident, which took place near the El Paso border crossing, is complicated by the fact that U.S. authorities, Mexican authorities and eyewitnesses all tell different accounts of the incident. The U.S. says the teen was with a group of youths who threw rocks at border agents while they were trying to arrest two illegal migrants. Mexican authorities have condemned the shooting, calling it excessive use of force.