One suspected illegal immigrant was detained on the levee on the U.S. side, the FBI said in a statement. Another Border Patrol agent arrived on the concrete bank where the now-dry, 33-feet (10-meter) wide Rio Grande is, and detained a second suspect. Other suspects ran back into Mexico and began throwing rocks, the FBI said.
At least one rock came from behind the agent, who was kneeling beside the suspected illegal immigrant who he had prone on the ground, FBI spokeswoman Andrea Simmons said.
The agent told the rock throwers to stop and back off, but they continued. The agent fired his weapon several times, hitting one who later died, said the FBI, which is leading the investigation because it involved an assault on a federal officer. The agent was not injured, Simmons said.