Hundreds of protesters closed streets and clashed with police around the Pacific Amphitheater in Costa Mesa Thursday night following Donald Trump's first campaign rally in Southern California.

Orange County police wore full riot gear, and some were on horseback as they clashed with a crowd of mostly anti-Trump protesters, who held Mexican flags and signs that denounced Trump's views on immigration.

The protest took shape as Trump's rally was ending at about 9 p.m. and the Republican presidential candidate's supporters walked to their cars. Anti-Trump protesters, who mostly waited outside during the rally, began gathering in larger numbers on the surrounding streets. While most of them were peacefully protesting, others became more violent. One man was seen atop a police car, while others threw rocks and broke police car windows.

Tweet: Broken police window

As helicopters circled overhead, police made a perimeter around the amphitheater parking lot to get the crowd to disperse at about 10 p.m. Seventeen people were arrested, and no one was seriously injured, according to Costa Mesa police. 

The protests came after Trump spoke for more than an hour to thousands of supporters as he kicked off his campaign for California's June primary. While some have speculated that Trump might be toning down his campaign rhetoric, Thursday night's speech was a return to many of the points he's made for months on the trail. He taunted his rivals, talked torture to combat terrorism, and pledged to build a wall on the Mexican border. 

He took special note of the rising L.A. murder rate.

"In this area, crime has increased 33 percent in the last year. What the hell is going on? I know what’s going on,” he told the crowd.

He attributed it to an increase in illegal immigration from Mexico, though research shows that not to be true. 

Smaller clashes took place earlier this afternoon between Trump supporters and detractors before his speech began. The rally drew thousands to the Orange County fairgrounds. 

The protest comes just days after Trump supporters and anti-Trump protesters clashed at an Anaheim City Council meeting where a protester released pepper spray on two young girls.