Videos are emerging show the chaos Saturday night when spring break revelers and police clashed during the Deltopia party in Santa Barbara County.
One video shows hundreds of young people running down a street as police moved in.
Another video shows what appears to be tear gas smoke rising as police tried to break up the party.
This video from the Daily Nexus shows police clearing the scene:
This shows another view:
One of the officers hit by flying rocks, bottles and bricks sustained extensive injuries as he and other law enforcement personnel tried to break up the melee, authorities said.
Santa Barbara County Sheriff Bill Brown told KTLA that the university police officer was struck in the head by a backpack containing large bottles of alcohol while responding to the spring break party, dubbed "Deltopia," about 9:30 p.m. Saturday in Isla Vista.
“It knocked him down, split his forehead open to the point that he needed extensive suturing,” Brown said.
When an arrest was made, the crowd became unruly, officials said.
Several people threw rocks and bottles at officers and an unlawful assembly was declared, according to a statement from the Santa Barbara County Sheriff's Department. During the melee, street signs were ripped down, small fires were set and sheriff's department vehicles were damaged, authorities said.
At least 100 people were arrested and dozens hurt during the unrest, which lasted for several hours as partygoers and police clashed in the 6700 block of Del Playa Drive.
At least five deputies were injured, including one who was hit in the face with a brick, and dozens more people were sent to the hospital for related injuries, authorities said.
According to KEYT-TV in Santa Barbara, authorities used tear gas, pepper spray, flash-bang grenades and foam projectiles to control the crowd.
An estimated 15,000 people attended Deltopia.
After several hours, authorities said, officers were able to disperse the crowd and restore order.
Brown told KTLA that the situation could have been much worse if deputies had not acted quickly.
"There could've been, potentially, loss of life, many more injuries, much more property damage," he said.