Federal agents were patrolling the Rio Grande in an airboat between Laredo, Texas, and Nuevo Laredo, Mexico, in September 2012. They say a group of men in a park on the Mexican side of the river began throwing rocks at them.
"I just remember the boat. They started to shoot and they hit him in the heart, and he fell to the ground," says Priscila Arévalo, the daughter of one of the Mexican men. "We ran away. When we came back, my papa he was already dead."