Victor Barrio, 29, was killed in the ring on Saturday in Teruel, eastern Spain, the first matador to be gored to death since 1985.
He died in front of spectators in a bullfight broadcast live on television when his chest was pierced by the horn of Lorenzo, a 500 kilogram (1,100 pound) bull from Los Maños ranch.
WARNING: Graphic footage of the moment bullfighter is gored to death.
The killer bull, whose name joins a list of ‘toros locos', was later slaughtered and taurine tradition dictates that the mother of a killer bull must also be sacrificed to kill off the bloodline.
But a campaign has been launched in an attempt to save the mother of the bull, who is named Lorenza.
The hashtag ‘Save Lorenza' - #SalvemosALorenza - became a trending topic on Twitter in Spain with hundreds signing a petition calling for the death to be averted.
The animal rights political party, Pacma, said the tradition highlighted the barbarity of bullfighting.
“The mother of Lorenzo, the bull they call the murderer, is being sent to slaughter to end the race,” Silvia Barquero, the president of Pacma, told The Local.
“No ritual, custom or tradition based on the succession of deaths, fed by blood or hatred, can be healthy for any society. We know only one ethical end to all this: the total abolition of all bullfights."
She added: “We reject the traditions based on violence, vengeance and blood.”
However, Spain's ABC newspaper claimed that Lorenza had in fact died a few days ago of "old age".