Fourth of July descended into mayhem across Southern California as unruly crowds overwhelmed packed-out fireworks displays, looted stores, ignited fires and saw cops charge on horseback. The worst unrest erupted in Newport Beach, where Independence Day revelers poured into Orange County, choking traffic and triggering a police response as disorder spread near the pier. Authorities ultimately shut down businesses from the Newport Pier to Pacific Coast Highway as officers moved in to restore order. Officers were swarmed by hundreds of people who hurled bottles and other debris at them before the crowd turned on one another and began fighting. Mounted...