Shortly after 7 p.m. on Thursday April 28, 2016, Republican presidential candidate Donald Trump spoke to supporters and attendees at a rally held at the Pacific Amphitheatre, at the OC Fair and Event Center in Costa Mesa. The Amphitheatre filled to capacity, permitting 8,200 attendees into the venue. An additional 3,000 visitors wishing to attend the event were turned away from the Event Center. Numerous protestor groups organized outside the OC Fair and Event Center property along Fairview Road and Fair Drive.

During the rally, protestor groups crowded the intersection at Fair Drive and Fairview Road and several motorists at the intersection deliberately spun their car tires in a reckless manner, posing a hazard to nearby pedestrians. Due to the swelling crowds and aggressive activity, mutual aid assistance was requested, activating officers from numerous surrounding agencies to provide emergency assistance.

Costa Mesa Police officers coordinated primarily with  Orange County Sheriff’s deputies and CHP officers to suppress potential violence outside the OC Fair and Event Center. Costa Mesa Police officers declared the crowd an unlawful assembly and gave several dispersal orders before giving the crowd ample time to disperse.

Costa Mesa Police officers  in protective riot gear, alongside Orange County Sheriff’s mounted deputies, and CHP officers worked collectively to clear Fair Dr. and surrounding streets of unruly crowds, and to keep access to the 55 freeway clear.

Donald Trump exited the area by 9:30 p.m., and mutual aid police agencies’ officers successfully dispersed all crowds by 11 p.m.

A total of 17 adults were arrested by Costa Mesa Police officers for failing to disperse. Those individuals were booked at the Costa Mesa Police Department jail and later released on written promises to appear.