There were fights and a police cruiser was damaged.

Protesters and supporters clashed in the streets of Costa Mesa on Thursday night after a Donald Trump rally. 

About 20 people were arrested, according to the Orange County Sheriff's Department. 

The GOP presidential frontrunner spoke at the OC Fair & Event Center, which is the area where the unruly crowd gathered.

Post Trump Rally protests in street at Fair&Fairview CM- law enforcement attempting to disperse crowd. No arrests pic.twitter.com/aJT4HGzepK

— OC Sheriff, CA (@OCSD) April 29, 2016

Video from the clash showed some fights among the crowd and property damage done, including the windows of a police cruiser being broken out. 

Police officers in tactical and riot gear were deployed to the area to control the crowd, video footage showed.  

Rojelio Banuelos, a 26-year-old student, carrying a sign that read, "Liberation not deportation" told CNN, "I'm against Trump's nativist and nationalistic agenda, which divides people and is very hateful of the other."

People jumping on police car outside @realDonaldTrump rally. Window smashed few minutes earlier pic.twitter.com/SOsFarQEVr

— Jeremy Diamond (@JDiamond1) April 29, 2016