Cesar Flores, 48, was shot three times, in the head, chest and neck, by the attacker who is still at large and being hunted by authorities.
Another player was also shot in the chest but survived – 25-year-old Walter Zarate was rushed to hospital but is said to be recovering.
The incident, which took place in Campo de la Bribera, the provincial capital of Cordoba, Argentina, on Sunday, saw the man run onto the pitch and pull a gun from his backpack as the game was being played.
“It all happened during the match,” police spokesman told the Efe news agency. “We don’t know what happened with the referee but the player was angry and went to get his gun and killed him.”