Demonstrators jumped on a Costa Mesa police car, breaking out the windows and attempting to turn it over, as tensions escalated after a Donald Trump rally on Thursday night.

Orange County Sheriff’s deputies were threatening to arrest hundreds of people who filled an intersection chanting, “Whose streets? Our streets!” as a large crowd poured out of the Pacific Amphitheatre. The crowd eventually dispersed by 11 p.m.

Earlier, authorities said the crowd was declared an “unlawful assembly” and ordered people to disperse. Police, some in full riot gear, were pushing the crowd east on Fair Drive toward the 55 freeway. But CHP officers were there to keep the freeway clear.

There were no major injuries.

Costa Mesa Police made 17 arrests on misdemeanor charges of failing to disperse, the agency said.

The California Highway Patrol arrested a man on suspicion of felony vandalism for allegedly throwing a rock at a patrol car, said Sgt. Phil Apodaca.

Several streets were temporarily blocked.

Protesters at one point moved toward deputies at Fairview Road and Fair Drive, who were wearing riot gear and displaying weapons loaded with “nonlethal ammunition.”

Officers including from Huntington Beach, Westminster, Laguna Beach, Irvine and Brea joined O.C. deputies and Costa Mesa police at the scene. A reporter saw five helicopters circling the commotion.

O.C. Sheriff’s Department Lt. Mark Stichter said 200 officers were on the scene.

The disturbance followed a buoyant Trump rally inside the venue that drew more than 8,000 people, most of them enthusiastic supporters. And there were no reports of clashes inside the open-air theater, which had the feel of a summer rock concert. The crowd stood and chanted its approval of the GOP front-runner’s message.

But Ian Smith, 24, who was inside the Trump rally, said it was filled with hate. He came out and saw hundreds in the street.

“There is so much passion,” said Smith of Chino Hills. “We’re the new guard. This is our country now.”

Some in the crowd also broke out portable speakers, blasting music and starting a mosh pit in the middle of the street. Others shouted profanities about Trump. Many waved Mexican flags.

“I’m willing to be arrested,” said Blanca Melchor, 18, of Anaheim. “I’m proud. We have a voice. This is because of Trump and what he says.”

Several protesters urged peace. Others seemed to want confrontation. Led by a woman with a megaphone, many protesters shouted, “Police and the Klan go hand in hand!”

One protester climbed the traffic light on the northeast corner of Fairview Road and Fair Drive, and wrote, “(Expletive) Trump.” The protesters cheered.

“This is the beginning of a movement,” said Chris Luna, 24, of Tustin. “Trump can’t take away our country.”