Donald Trump's rally in Costa Mesa, California, was marked by violent protests from "almost entirely Latino" individuals, many waving Mexican flags, that led police to arrest at least 20 – though eyewitnesses said supporters of the billionaire businessman were all peaceful and the swell of aggression stemmed solely from the opposition camps.

"The Trump supporters were the peaceful people singing patriotic songs, festive and happy, while the protesters were very angry and high aggression," one rally attendee, Terry Krokosz, told Breitbart.

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He described the scene as chaotic due to a crowd of 70 or so protesters that quickly grew into the hundreds.

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The agitators swarmed the intersection outside the Pacific Amphitheatre and blocked traffic, the Los Angeles Times reported.

"They were very aggressive," Krokosz said. "When we were leaving, there were a lot of people in cars, Mexican flags hanging out the windows. A guy was doing donuts and the intersection was shut down. We saw people marching through the intersection."

A police car was seen with smashed windows and a person was jumping up and down on top of the vehicle. Another person wrote "F--k Trump" on a police cruiser, and others slashed a police SUV's tires and tried to overturn another law-enforcement vehicle.

A Los Angeles Times reporter posted a photograph of a man with a bloodied face wearing a Trump shirt on Twitter. Journalist Matt Pearce tweeted, with the photo: "Trump supporter got hurt."

Pearce also put out on Twitter several other messages describing the scene.

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In one tweet, Pearce wrote: "Trump supporter Colby Nicholson, watching the action in a Trump hat: 'These are all underage Mexican high schoolers who have nothing to do."

In another, he wrote, quoting a protester at the scene: "Juan Carlos, 16: 'Donald Trump is worthless! There won't be no United States without Mexicans.'"

And another: "Couple hundred people here blocking the streets outside Trump rally. Mostly younger. Almost entirely Latino/Latina."

And in yet one more, Pearce citing another protester at the scene: "Arianna Perez, 19, with the sign: 'We could be peaceful & do things different, but we wouldn't get our voice heard.'"

Officers arrested 20, as hundreds blocked traffic on the Costa Mesa streets, located just south of Los Angeles, and smashed a police car, NBC News reported.

Fights broke out all over, with protesters chanting the likes of "racists go home" at the Trump supporters, and "Whose streets? Our streets," while at least one driver began spinning donuts in the middle of the street action, NBC said.

Jose Cruz, 21, told the Los Angeles Times that the protests reflected “the anger people have against Trump.”

One eyewitness took to Twitter to post a video of the wrecked police vehicle, which protesters then jumped upon, and wrote: "Protesters just wrecked this cop car. Bashed in windows, jumping on top of it."

Orange County Sheriff's officials reported nobody was injured.

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In a tweet, the sheriff's office wrote: "Post Trump Rally Protest over. Approx 20 arrests by Costa Mesa PD. No major injuries. Crowd dispersed by 11pm. No further updates."

In March, a protest at a Trump rally that was planned but canceled in Chicago wrapped in physical violence and chaos, with several fights breaking out between candidate supporters and opponents.

The violence Thursday night in Orange County took place as Trump addressed a crowd of thousands during his first rally in California, where he honored the families of those killed by illegal aliens.

Trump was joined on stage by Jamiel Shaw, whose son was murdered by an illegal alien in 2008, as well as with other members of the Remembrance Project.

"They're unbelievable, they've suffered," Trump said before bringing them up on the stage. "These are great people."

Trump also said, various media reported: "They all have a very similar story to tell. People that shouldn't have been here, people that should have never been allowed to come over the border and they come here like its nothing, they walk through it like its nothing."

Taking the microphone, Shaw reiterated Trump's "make America great" mantra.

"We demand Americans first," he said. "We don't care about illegal aliens."

Attendees, meanwhile, cheered.

"Build the wall," they chanted.

And Trump's response?

"We're going to stop it and we're going to build a wall," he said, speaking of illegal immigration.