Los Angeles (CNN)A social media post telling people to show up to a party in Huntington Beach led to the unlawful assembly of more than 2,500 people, police said.
Police in the Southern California city said they knew about the post and made preparations, but the crowd became "unruly" Saturday night -- prompting the declaration of an unlawful assembly.
"The initial crowd at the beach grew in size and moved to the downtown area where it was estimated to be over 2,500," the Huntington Beach Police Department said in a statement.
"As the crowd size continued to grow rapidly, large groups disbursed into various locations throughout the area, throwing bottles, rocks, fireworks, and other items at officers. At that time, the HBPD requested assistance from outside agencies. Throughout the course of the evening, over 150 officers from virtually all agencies within Orange County were deployed to Huntington Beach based on the pre-arranged request for assistance."
Multiple downtown businesses, police vehicles and a lifeguard tower were damaged due to vandalism, authorities said.
An emergency curfew was issued from 11:30 p.m .Saturday until 5:30 a.m. Sunday for parts of Huntington Beach, police said.
By the time the chaos ended, 121 adults and 28 juveniles were arrested and booked for charges such as vandalism, the firing of dangerous/illegal fireworks, failure to disperse and curfew violations, police said.
No significant injuries have been reported.
Huntington Beach resident Natalie Rosso said it's not uncommon for a social media post to draw massive crowds to the coastal community, about 35 miles southeast of Los Angeles.
"When something goes viral in Huntington Beach it always brings the biggest crowds that are crazy," Natalie Rosso posted along with a video on Instagram.
"You can't even drive down the street now."
Afterward, Rosso told CNN she was "disappointed" by what happened.
She said she's lived in Huntington Beach her "whole life and have never seen anything like that before."