More than 400 people are arrested following a chaotic Fourth of July celebration in Newport Beach, California, according to multiple reports. Coverage describes the event escalating into disorder amid scenes reported as riots and explosions. Reports state that police deploy in large numbers, including horse-mounted officers, as authorities respond to disturbances during the holiday. One outlet reports 400 arrests, while another specifies 402 arrests, indicating a similar overall arrest count. The reports characterize the incident as a sudden spiral from a holiday gathering into unrest, with law enforcement actions focused on detaining people amid ongoing disruption. Both sources agree on the location—Newport Beach, California—the timing—July 4 celebrations—and the overall scale of arrests, with roughly 400 people taken into custody. Details about the specific causes of the violence, the charges filed, or whether any injuries occurred are not provided in the excerpts.