The shocking incident happened at the weekend during a regional league match near Belo Horizonte, with amateur side Brumadinho playing against Amantes da Bola.
Following a disputed red card offence, the referee was apparently kicked by the player he'd given the card to. He marched off to the changing rooms before bringing back out a gun and confronting the player.
The official who believe it or not is a police officer by day, had to be restrained by one of the other linesmen. He is due to undergo a psychological assessment on Tuesday and could face suspension or a permanent ban.