FBI: Mexicans chased away agents after slaying The death is the second in two weeks involving agents http://www.msnbc.msn.com/id/37598115/ns/world_news-americas/ CIUDAD JUAREZ, Mexico - Pointing their rifles, Mexican security forces chased away U.S. authorities investigating the shooting of a 15-year-old Mexican by a U.S. Border Patrol agent on the banks of the Rio Grande, the FBI and witnesses told The Associated Press on Wednesday. The killing of the Mexican by U.S. authorities the second in less than two weeks has exposed the distrust between the two countries that lies just below the surface, and has enraged Mexicans who see the death of the boy on Mexican soil as an act of murder. Shortly after the boy was shot, Mexican soldiers arrived at the scene and pointed their guns at the Border Patrol agents across the riverbank while bystanders screamed insults and hurled rocks and firecrackers, FBI spokeswoman Andrea Simmons said. She said the agents were forced to withdraw. A relative of the dead boy who had been playing with him told the AP that the Mexicans who he described as federal police, not soldiers pointed their guns only when the Americans waded into the mud in an apparent attempt to cross into Mexico. The Mexican authorities accused the Americans of trying to recover evidence from Mexican soil and threatened to kill them if they crossed the border, prompting both sides to draw their guns, said the 16-year-old boy who asked not to be further identified for fear of reprisal. U.S. authorities said Tuesday a Border Patrol agent was defending himself and colleagues when he fatally shot the 15-year-old as officers came under a barrage of big stones while trying to detain illegal immigrants on the U.S. side of the Rio Grande. About 30 relatives and friends gathered late Tuesday to mourn Sergio Adrian Hernandez Huereka, who died Monday on the Mexican side of the river border with Texas. "Damn them! Damn them!" sobbed Rosario Hernandez, sister of the dead teenager, at a wake in the family's two-room adobe house on the outskirts of Ciudad Juarez. Preliminary reports on the incident indicated that U.S. officers on bicycle patrol "were assaulted with rocks by an unknown number of people," Border Patrol Special Operations Supervisor Ramiro Cordero said Tuesday. "During the assault at least one agent discharged his firearm," he said. "The agent is currently on administrative leave. A thorough, multi-agency investigation is currently ongoing."