A fan rally to celebrate the San Diego Chargers’ 2013 season turned violent on Sunday after a fight broke out between a group of people and a lone Denver Broncos fan.

In the wake of the San Diego’s 24-17 loss to the Broncos on Sunday, a group of Chargers fans gathered in San Diego County's National City to commemorate their team’s season, the Denver Post reports. At some point during the rally, a fight broke out between a lone Broncos fan and group of Chargers fans. Chris Biele, a reporter for Fox 5 San Diego, was present for the fight and posted details of the incident to his Twitter account.

“Mostly peaceful [Chargers] rally in National City except for one incident. 1 [Broncos] fan and 3 [Chargers] fans arrested after fight,” Biele wrote. “[Broncos] fan came in like he owned the place and [Chargers] fans didn’t like that.”

In a viral video of the incident, the Chargers fans can be seen beating up the Broncos fan. It’s unclear what prompted the brawl, but a man wearing a Chargers jersey exchanged a series of punches with the Broncos fan. The Broncos fan got knocked to the pavement, prompting a second Chargers fan to enter the fracas. The two men delivered several punches and kicks to the fallen Broncos fan before police arrive to break up the fight.

A subsequent report by Fox 5 San Diego confirms that local police arrested three Chargers fans and one Broncos fan. In addition, a photographer from a local television station suffered a bite from a police dog and was treated for minor injuries at the scene, Fox 5 reports.

San Diego-area police have yet to determine the cause of the fight. It’s also unknown if any of the individuals involved in the fight suffered any injuries.