The unidentified player shot César Flores three times after being shown a red card during a game in the Córdoba province.
Flores, 48, was shot in the head, chest and neck, while another player was also shot, but is understood to be recovering.
“It all happened during the football match,” said a police source, reported The Guardian.
“We don’t know [exactly what took place], but it appears the player was angry, fetched a gun and killed him.”
Police are now hunting the player who has disappeared.
Violence is not uncommon during the country’s soccer games, and last month five players were sent off during a pre-season game between River Plate and Boca Juniors in Buenos Aires.