The violence happened Sunday morning near Livingston.
Sheriff's detectives say a man, who has not yet been identified, shot and killed 20-year-old Miguel Orosco over a $10 cockfighting bet.
Then, deputies say the shooting victim's brother Rafael Orosco and another man Juan Aguilera chased the shooter into the street and beat him to death.
Both are under arrest.
A statement issued by the Humane Society of The United States calls for tougher cockfighting punishments in California saying "it is time to make cockfighting a felony on the first offense so we can deter cockfight promoters from staging these events."
California is one of only ten states where cockfighting is still considered a misdemeanor for the first offense.