Eight people were arrested Sunday night in Huntington Beach, California after a rash of mob violence following the conclusion of a surfing competition, KABC-TV reported.

"People started getting a riot mentality, and things started getting crazy," one witness told KABC. "And then on Main Street, people started pushing over porta-potties, jumping on the porta-potties, then they started breaking things in the street."

Local police told KABC the unrest began around 7:15 p.m. local time, about two hours after the end of the annual U.S. Open of Surfing event, when large fights broke out among the crowd of spectators, with the disturbances moving into the city's downtown area as police moved in to disperse the revelers. Departments from nearby cities were called in for assistance, forcing streets to be closed down until the crowd was cleared out around 10 p.m.

"We’re extremely disappointed and saddened by the disturbance that occurred up on Main St [sic] after the close of the US Open of Surfing," event organizers wrote on Facebook Sunday night. "We work tirelessly with City staff, police, fire and other agencies to ensure a safe environment for all. We appreciate the quick response of HBPD and are awaiting further information."

Watch KABC's report, aired Sunday night, below.

[h/t LA Weekly]