Attacking midfielder Carlos Alcaraz sparked a commotion in front of Boca fans by celebrating the winner,
Boca Junior took the lead in the 19th minute at Estadio Parque La Pedrera through Norberto Briasco, but leveled the score shortly after thanks to a Matias Rojas goal.
No more goals were scored during the first 90 minutes, meaning the game went into extra time.
And with just two minutes remaining before the game ended or the penalty shootout, Alcaraz scored the winner, heading Gonzalo Piovi's cross past goalkeeper Agustin Rossi.
Alcaraz's long celebration in front of the opposing fans angered the Boca players and chaos ensued.
Two Boca Juniors players and one from Racing – Sebastian Villa, Johan Carbonero and Alan Varela – have been sent off at this point.
Alcaraz went on to become the fourth player to receive a red card, before six more players followed suit for an early celebration.
Two additional players leave the field after receiving a second yellow card. For the parts. Racing Club had two additional players sent off for direct reading - Carlos Alcaraz and Catriel Cabellos.
The home side had another six players sent off in subsequent extra time, with four players - Louis Advincula, Carlos Zambrano, Diego Gonzalez and Dario Benedetto - all straight red cards.
By the time the referee blew full time in Racing's 2-1 win, the field had 12 players left on it.