Protests have been a regular fixture inside and outside of Donald Trump's rallies pretty much since the start of his candidacy.

And while many of them are nonviolent, a few have turned really, really ugly.

Sometimes protesters clash with police. But other times, in perhaps a more volatile mix, they clash with Trump supporters. That was the case Thursday night in San Jose, where peaceful protests turned violent as anti-Trump protesters and Trump supporters met in the streets. One group of protesters is seen grabbing cardboard Trump signs and ripping them apart as other protesters exchange punches with Trump fans. In another clip, protesters carrying American and Mexican flags kick Trump supporters. "Make America Great Again" hats were burned on the street. And photos show a woman being pelted with eggs as she left the rally.

It's a pattern that has a lot of onlookers worried: violence at (or outside of) Trump events that escalates when supporters and protesters meet. And Trump has been accused of excusing or even provoking violence against protesters at his rallies. It's just one of the reasons there are concerns about July's Republican National Convention in Cleveland, which is sure to draw protesters.