He had ties to the anarchosyndicalist labor organization, the Casa del Obrero Mundial "House of the World Worker.
After demonstrating his talent, Murillo was awarded a grant in 1897 by the government of Porfirio Díaz to study painting in Europe.
There he broadened his scope of learning, with study of philosophy and law at the University of Rome, and many trips to Paris to hear lectures on art given by Henri Bergson.
In Paris, he founded a journal and wrote about the social and political issues of Mexico, and criticized General Victoriano Huerta, who had helped overthrow the democratically elected government of Francisco I. Madero.
Dr. Atl supported the Constitutionalist faction in the Mexican Revolution, leaning towards "biblical socialism" and promoting the growth of art, literature, and science.
When he returned from Europe, he joined the Constitutionalist forces led by Venustiano Carranza, and was appointed Director of the Academy of San Carlos.
The plot description states: "On the run from the authorities, Atl (played by David J. Stewart) takes refuge in a convent that is allegedly haunted by the ghost of an Aztec warrior.
Dr. Atl died in Mexico City in 1964 and is buried in Panteon Civil de Dolores cemetery in the capital.