Boca Junior's flags during match against River Plate in Mendoza, Argentina, 2013. Photo from user Rogerio Tomaz Jr. (CC BY-NC 2.0)

Argentina's two most famous football clubs and the bitterest of rivals, Boca Juniors and River Plate, squared off in a round of 16 match in the Copa Libertadores, South America's premier club football tournament, on May 14. Despite the intense build-up and millions of viewers, only the first half of the match was played at Boca Juniors's Alberto J. Armando stadium.

At the start of the second half, as River Plate's players were coming back onto the pitch, four of them were attacked with a toxic material used in the manufacturing of pepper spray. This would eventually lead to the abandoning of the most eagerly anticipated match of this year's tournament, organized by CONMEBOL, South American football's governing body.

Within five days of the attack, a group of Boca's supporters were identified as the culprits using the stadium's security camera footage, with the main offender named as lifelong fan Adrián Napolitano. Prosecutor Susana Calleja issued the summons for Napolitano for questioning, but stopped short of requesting his arrest

However, in the hours and days immediately following the match, debate had raged as to whether it was indeed a fan or even if it was the police themselves. Following the match, the hashtag #FueLaPolicia (it was the police) quickly started trending.

Si #FueLaPolicia ¿Berni lo va a admitir? ¿los periodistas van a pedir perdon a los hinchas genuinos de boca? siga,siga la joda….

— Paatsy (@Mypaatsy) Mayo 15, 2015

If it was the police, will [Argentina's security chief Sergio] Berni admit it? Will the journalists apologize to Boca's fans? Let the joke continue…

Siguen llorando los bosteros? Encima que entraron por la ventana a la copa hacen cagadas #SuperVerguenza #FueLaPolicia ? Jajaja — Te Amo River (@Sebaferri13) Mayo 16, 2015

Are the bosteros [negative term for Boca's fans] still crying? On top of getting into the tournament through the back door, they cause shit. Total embarrassment.
It was the police ? Hahaha

#SiempreConVosCABJ Digan lo que digan, siempre el mas grande! #FueLaPolicia dejen de echar la culpa a los hinchas.

— Kenia Moreno (@AsqMoreno) Mayo 16, 2015

Always with you Club Atletico Boca Juniors. Say what they will, always the best! Stop blaming the fans.

Mas alla si #FueLaPolicia o no, lo grave es todo lo que pasó después. Las 2hs para suspender el partido, q los jugadores no puedan irse…

— Fabricio (@fabrisino) Mayo 15, 2015

Whether it was the police or not, the serious part is what happened after. The two hours waiting to abandon the match, where the players couldn't leave…

La Bombonera, as Boca Juniors’ stadium is known, was at full capacity during the match, which was attended only by members and supporters of the home club; visiting fans have been banned from football matches in Argentina since the death of a spectator in 2013.

“La 12″, another name for Boca Juniors’ legion of fans, was chosen as the best following in the world by the French football magazine So Foot. Boca is itself one of the most successful clubs in South American and indeed world football, with six Copa Libertadores, four South American Super Cups, two South American Cups, and three Intercontinental Cups to their name. The club has also given rise to superstars such as Diego Armando Maradona, Carlos Tévez, and Juan Román Riquelme, among others.

During the nearly two hours that passed before the referee finally decided to abandon the match, Boca fans flew a drone carrying a banner with the letter B (making fun of River Plate’s 2011 relegation to Argentina's second tier league, the Primera B) across the stadium:

The majority of spectators had left the stadium, but both teams waited longer to leave the field of play for the locker rooms, since a group of fans repeatedly threw plastic bottles at the River Plate players each time they approached the sleeve leading back into the clubhouse.

As if this wasn't enough, and to further fuel the controversy, the Boca Juniors players stayed on the pitch after their opponents had left, and saluted the fans that were still in the stadium:

#Boca ,te están matando!! Pensar que había gente que decía “El problema es Riquelme”. Ya no tienen a quien culpar. #Orion aplaude a la barra

— Gonza (@Gonzalo_Erguy) Mayo 15, 2015

Boca, they're killing you! To think that people were saying “the problem is Riquelme”. They don't have anyone left to blame. [Boca's goalkeeper] Orion applauds the crowd

Esta imagen pasará a la historia como uno de los actos mas estúpidos del futbol mundial #ParaLaHistoria #Orion pic.twitter.com/KSJfNDgoYl

— Anibal Avendaño (@anibal86co) Mayo 15, 2015

This image will go down as one of the stupidest acts in the history of world football.

The decision from CONMEBOL:

Two days later, the hashtag #LaSancionABoca (the sanction against Boca) quickly began trending after CONMEBOL announced the punishment that would be handed down to Boca Juniors: Boca would be eliminated from the 2015 Copa Libertadores, and River Plate plate would advance to the quarter-finals, where they meet Brazilian club Cruzeiro:

Comunicado oficial caso Boca-River. pic.twitter.com/kPbKLFR3xs

— CONMEBOL.com (@CONMEBOL_CSF) Mayo 17, 2015

Official press release on the Boca-River case

The responses from both sets of fans spread on social media:

Sale más caro una multa por cruzar en rojo un semáforo que #LaSancionABoca

— ├ MǾĻΞŠΤĨЄ ┤ (@molestie) Mayo 17, 2015

The fine for crossing on a red light is more expensive than the sanction against Boca

Che vieron las sanciones de #CONMEBOL? #LaSancionABoca pic.twitter.com/XEkHTUrhF4

— Nicolás de León (@salocinuy) Mayo 17, 2015

Hey, did you guys see the sanctions from #CONMEBOL?

LA SACAMOS RE BARATA, NADA QUE VER LO QUE DECIAN #LaSancionABoca

— roro✨ ¦ boca juniors (@styIesp4radise) Mayo 17, 2015

WE GOT OFF EASY, NOTHING TO DO WITH WHAT THEY WERE SAYING

Nos eliminaron injustamente, el equipo no tiene la culpa y RiBer exagero los síntomas #LaSanciónABoca #Boca

— Roma (@RomaPozzuto) Mayo 17, 2015

They eliminated us unfairly, it's not the team's fault and RiBer [negative term for River Plate] exaggerated the symptoms

Ustedes nos dejaron 5comentarios Y NOSOTROS LOS DEJAMOS 5COPA LIBERTADORES JAJAJAJAJAJAJA #LaSancionABoca #BostaJuniors

— ♛60%73%♥VOT2luz❤ (@Rusher_Gallina_) Mayo 16, 2015

You leave us 5 comments and WE LEAVE YOU 5 COPA LIBERTADORES HAHAHAHA!

Another trending tag among Boca fans was #DisculpaRiver [Sorry River], with many expressing their  disgust with other fans from their own club:

Soy una verdadera hincha de Boca. Repudio la violencia #DisculpaRiver #NoMasViolencia pic.twitter.com/V8ZfF2ppgT

— Mariné Moreno (@MMaruMMoreno) May 15, 2015

I am a true Boca fan. I condemn violence. [Sorry River] [No more violence]

According to CONMEBOL's decision, the Boca Juniors will have to play its next four home games in CONMEBOL tournaments behind closed doors, while its fans will not be able to travel to any of its next four away matches.