Chavez is the father of Jason, a friend of Antonio's. Early in the novel Bless Me, Ultima, Chavez' brother is killed by Lupito, a World War II veteran suffering from Post Traumatic Stress Disorder. While everyone knows Lupito's head isn't right since the war, Chavez cannot let the killing of his brother go unanswered, and in his own fit of mourning and rage, Chavez is the one who rounds up a posse to go after Lupito, finally trapping him by the river and ultimately killing him.
This is an important scene in the book as it is Tony's first close up view of death, and the first of several in the story. He feels sorry for Lupito, and this preares him for his upcoming experiences with Ultima.